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

The matrikine N-acetylated proline-glycine-proline induces premature senescence of nucleus pulposus cells via CXCR1-dependent ROS accumulation and DNA damage and reinforces the destructive effect of these cells on homeostasis of intervertebral discs

AbstractIntervertebral disc (IVD) cell senescence is a recognized mechanism of intervertebral disc degeneration (IDD). Elucidating the molecular mechanisms underlying disc cell senescence will contribute to understanding the pathogenesis of IDD. We previously reported that N-acetylated proline-glycine-proline (N-Ac-PGP), a matrikine, is involved in the process of IDD. However, its roles in IDD are not well understood. Here, using rat nucleus pulposus (NP) cells, we found that N-Ac-PGP induced premature senescence of NP cells by binding to CXCR1. N-Ac-PGP induced DNA damage and reactive oxygen species accumulation in NP cells, which resulted in activation of the p53-p21-Rb and p16-Rb pathways. Moreover, the RT2 profiler PCR array showed that N-Ac-PGP down-regulates the expression of antioxidant genes in NP cells, suggesting a decline in the antioxidants of NP cells. On the other hand, N-Ac-PGP up-regulated the expression of matrix catabolic genes and inflammatory genes in NP cells. Concomitantly, N-Ac-PGP reinforced the destructive effects of senescent NP cells on the homeostasis of the IVDs in vivo. Our study suggests that N-Ac-PGP plays critical roles in the pathogenesis of IDD through the induction of premature senescence of disc cells and via the activation of catabolic and inflammatory cascades in disc cells. N-Ac-PGP also deteriorates the redox environment of disc cells. Hence, N-Ac-PGP is a new potential therapeutic target for IDD

Power-controlled acoustofluidic manipulation of microparticles

Recently, surface acoustic wave (SAW) based acoustofluidic separation of microparticles and cells has attracted increasing interest due to accuracy and biocompatibility. Precise control of the input power of acoustofluidic devices is essential for generating optimum acoustic radiation force to manipulate microparticles given their various parameters including size, density, compressibility, and moving velocity. In this work, an acoustophoretic system is developed by employing SAW based interdigital electrode devices. Power meters are applied to closely monitor the incident and reflected powers of the SAW device, which are associated with the separation efficiency. There exists a range of input powers to migrate the microparticles to the pressure node due to their random locations when entering the SAW field. Theoretical analysis is performed to predict a proper input power to separate mixtures of polystyrene microspheres, and the end lateral position of microspheres being acoustically separated. The separation efficiency of four sizes of microspheres, including 20 µm, 15 µm, 10 µm, and 5 µm, is calculated and compared with experimental results, which suggest the input power for separating the mixture of these microspheres. The study provides a practical guidance on operating SAW devices for bioparticle separation using the incident power as a control parameter

DEP and AFO Regulate Reproductive Habit in Rice

Sexual reproduction is essential for the life cycle of most angiosperms. However, pseudovivipary is an important reproductive strategy in some grasses. In this mode of reproduction, asexual propagules are produced in place of sexual reproductive structures. However, the molecular mechanism of pseudovivipary still remains a mystery. In this work, we found three naturally occurring mutants in rice, namely, phoenix (pho), degenerative palea (dep), and abnormal floral organs (afo). Genetic analysis of them indicated that the stable pseudovivipary mutant pho was a double mutant containing both a Mendelian mutation in DEP and a non-Mendelian mutation in AFO. Further map-based cloning and microarray analysis revealed that dep mutant was caused by a genetic alteration in OsMADS15 while afo was caused by an epigenetic mutation in OsMADS1. Thus, OsMADS1 and OsMADS15 are both required to ensure sexual reproduction in rice and mutations of them lead to the switch of reproductive habit from sexual to asexual in rice. For the first time, our results reveal two regulators for sexual and asexual reproduction modes in flowering plants. In addition, our findings also make it possible to manipulate the reproductive strategy of plants, at least in rice

Removal of Trichloroethylene from Water by Bimetallic Ni/Fe Nanoparticles

Chlorinated organic solvents (COSs) are a significant threat to human beings. In this study, nanoscale bimetallic Ni/Fe particles were synthesized from the reaction of sodium borohydride (NaBH4) with the reduction of Ni2+ and Fe2+ in an aqueous solution. The synthesized nanoscale zero-valent iron (nZVI) and Ni-nZVI were characterized by SEM (scanning electron microscopy), XRD (X-ray diffractometer), Brunauer–Emmett–Teller (BET), and transmission electron microscopy (TEM). The removal performance of trichloroethylene (TCE) over the nZVI catalyst and Ni-nZVI was evaluated. Ni-nZVI with different Ni contents exhibited good reactivity towards the dechlorination of TCE over a 1h period, and the pseudo-first-order rate constant for TCE dechlorination by Ni-nZVI was 1.4–3.5 times higher than that of nZVI. Ni-nZVI with 5 wt% Ni contents exhibited the best dechlorination effect; the removal rates of TCE and its by-product dichloroethylene (DCE) were 100% and 63.69%, respectively. These results indicated that the Ni nanoparticles as the second dopant metal were better than nZVI for TCE degradation. This determination of the optimal Ni-NZVI load ratio provides a factual and theoretical basis for the subsequent application of nano-metal binding in the environment

Joint optimization of overlapping phases in MapReduce

ABSTRACT MapReduce is a scalable parallel computing framework for big data processing. It exhibits multiple processing phases, and thus an efficient job scheduling mechanism is crucial for ensuring efficient resource utilization. This work studies the scheduling challenge that results from the overlapping of the "map" and "shuffle" phases in MapReduce. We propose a new, general model for this scheduling problem. Further, we prove that scheduling to minimize average response time in this model is strongly NP-hard in the offline case and that no online algorithm can be constant-competitive in the online case. However, we provide two online algorithms that match the performance of the offline optimal when given a slightly faster service rate

Path Tracking Control of Autonomous Vehicle Based on Nonlinear Tire Model

The tire forces of vehicles will fall into the non-linear region under extreme handling conditions, which cause poor path tracking performance. In this paper, a model predictive controller based on a nonlinear tire model is designed. The tire forces are characterized with nonlinear composite functions of the magic formula instead of a simple linear relation model. Taylor expansion is used to linearize the controller, the first-order difference quotient method is used for discretization, and the partial derivative of the composite function is used for matrix transformation. Constant velocity and variable velocity conditions are selected to compare the designed controller with the conventional controller in Carsim/Simulink. The results show that when the tire forces fall in the nonlinear region, two controllers have good stability, and the tracking accuracy of the controller designed in this paper is slightly better. However, after the tire forces become nonlinear, the controller with linear tire force becomes worse, the tracking accuracy is far worse than the controller with the nonlinear tire model, and the vehicle stability is also degraded. In addition, an active steering test platform based on LabVIEW-RT is established, and hardware-in-the-loop tests are carried out. The effectiveness of the designed controller is verified

Joint Optimization of Overlapping Phases in MapReduce

MapReduce is a scalable parallel computing framework for big data processing. It exhibits multiple processing phases, and thus an efficient job scheduling mechanism is crucial for ensuring efficient resource utilization. There are a variety of scheduling challenges within the MapReduce architecture, and this paper studies the challenges that result from the overlapping of the “map ” and “shuffle ” phases. We propose a new, general model for this scheduling problem, and validate this model using cluster experiments. Further, we prove that scheduling to minimize average response time in this model is strongly NP-hard in the offline case and that no online algorithm can be constant-competitive. However, we provide two online algorithms that match the performance of the offline optimal when given a slightly faster service rate (i.e., in the resource augmentation framework). Finally, we validate the algorithms using a workload trace from a Google cluster and show that the algorithms are near optimal in practical settings.

TIPE2 negatively regulates inflammation by switching arginine metabolism from nitric oxide synthase to arginase.

TIPE2, the tumor necrosis factor (TNF)-alpha-induced protein 8-like 2 (TNFAIP8L2), plays an essential role in maintaining immune homeostasis. It is highly expressed in macrophages and negatively regulates inflammation through inhibiting Toll-like receptor signaling. In this paper, we utilized RAW264.7 cells stably transfected with a TIPE2 expression plasmid, as well as TIPE2-deficient macrophages to study the roles of TIPE2 in LPS-induced nitric oxide (NO) and urea production. The results showed that TIPE2-deficiency significantly upregulated the levels of iNOS expression and NO production in LPS-stimulated macrophages, but decreased mRNA levels of arginase I and urea production. However, TIPE2 overexpression in macrophages was capable of downregulating protein levels of LPS-induced iNOS and NO, but generated greater levels of arginase I and urea production. Furthermore, TIPE2-/- mice had higher iNOS protein levels in lung and liver and higher plasma NO concentrations, but lower levels of liver arginase I compared to LPS-treated WT controls. Interestingly, significant increases in IκB degradation and phosphorylation of JNK, p38, and IκB were observed in TIPE2-deficient macrophages following LPS challenge. These results strongly suggest that TIPE2 plays an important role in shifting L-arginase metabolism from production of NO to urea, during host inflammatory response