Different mechanisms underlying divergent responses of autotrophic and heterotrophic respiration to long-term throughfall reduction in a warm-temperate oak forest

Background:There are many studies on disentangling the responses of autotrophic(AR)and heterotrophic(HR)respiration components of soil respiration(SR)to long-term drought,but few studies have focused on the mechanisms underlying its responses.Methods:To explore the impact of prolonged drought on AR and HR,we conducted the 2-year measurements on soil CO_(2) effluxes in the 7th and 8th year of manipulated throughfall reduction(TFR)in a warm-temperate oak forest.Results:Our results showed long-term TFR decreased HR,which was positively related to bacterial richness.More importantly,some bacterial taxa such as Novosphingobium and norank Acidimicrobiia,and fungal Leptobacillium were identified as major drivers of HR.In contrast,long-term TFR increased AR due to the increased fine root biomass and production.The increased AR accompanied by decreased HR appeared to counteract each other,and subsequently resulted in the unchanged SR under the TFR.Conclusions:Our study shows that HR and AR respond in the opposite directions to long-term TFR.Soil microorganisms and fine roots account for the respective mechanisms underlying the divergent responses of HR and AR to long-term TFR.This highlights the contrasting responses of AR and HR to prolonged drought should be taken into account when predicting soil CO_(2) effluxes under future droughts.

Divergent allocations of nonstructural carbohydrates shape growth response to rainfall reduction in two subtropical plantations

Nonstructural carbohydrates(NSC)are indicators of tree carbon balance and play an important role in regulating plant growth and survival.However,our understanding of the mechanism underlying drought-induced response of NSC reserves remains limited.Here,we conducted a long-term throughfall exclusion(TFE)experiment to investigate the seasonal responses of NSC reserves to manipulative drought in two contrasting tree species(a broadleaved tree Castanopsis hystrix Miq.and a coniferous tree Pinus massoniana Lamb.)of the subtropical China.We found that in the dry season,the two tree species differed in their responses of NSC reserves to TFE at either the whole-tree level or by organs,with significantly depleted total NSC reserves in roots in both species.Under the TFE treatment,there were significant increases in the NSC pools of leaves and branches in C.hystrix,which were accompanied by significant decreases in fine root biomass and radial growth without significant changes in canopy photosynthesis;while P.massoniana exhibited significant increase in fine root biomass without significant changes in radial growth.Our results suggested that under prolonged water limitation,NSC usage for growth in C.hystrix is somewhat impaired,such that the TFE treatment resulted in NSC accumulation in aboveground organs(leaf and branch);whereas P.massoniana is capable of efficiently utilizing NSC reserves to maintain its growth under drought conditions.Our findings revealed divergent NSC allocations under experimental drought between the two contrasting tree species,which are important for better understanding the differential impacts of climate change on varying forest trees and plantation types in subtropical China.

Intrinsic V vacancy and large magnetoresistance in V_(1-δ)Sb_(2)single crystal

The binary pnictide semimetals have attracted considerable attention due to their fantastic physical properties that include topological effects, negative magnetoresistance, Weyl fermions, and large non-saturation magnetoresistance. In this paper, we have successfully grown the high-quality V_(1-δ)Sb_(2) single crystals by Sb flux method and investigated their electronic transport properties. A large positive magnetoresistance that reaches 477% under a magnetic field of 12 T at T = 1.8 K was observed. Notably, the magnetoresistance showed a cusp-like feature at the low magnetic fields and such feature weakened gradually as the temperature increased, which indicated the presence of a weak antilocalization effect(WAL). In addition, based upon the experimental and theoretical band structure calculations, V_(1-δ)Sb_(2) is a research candidate for a flat band.

外尔半金属砷化铌纳米带中的超高导电率

在二维体系中,高迁移率通常是在低电子浓度的半导体和半金属中实现的。本文作者发现,即使在高电子浓度情况下,外尔半金属砷化铌纳米带仍然保持着较高的迁移率。作者提出了一种合成具有可调谐费米能级的单晶砷化铌纳米带的方案。

Absence of metallicity and bias-dependent resistivity in low-carrier-density EuCd_(2)As_(2)

EuCd_(2)As_(2)was theoretically predicted to be a minimal model of Weyl semimetals with a single pair of Weyl points in the ferromagnet state.However,the heavily p-doped Eu Cd_(2)As_(2)crystals in previous experiments prevent direct identification of the semimetal hypothesis.Here,we present a comprehensive magneto-transport study of high-quality Eu Cd_(2)As_(2)crystals with ultralow bulk carrier density(10^(13)cm^(-3)).In contrast to the general expectation of a Weyl semimetal phase,Eu Cd_(2)As_(2)shows insulating behavior in both antiferromagnetic and ferromagnetic states as well as surface-dominated conduction from band bending.Moreover,the application of a dc bias current can dramatically modulate the resistance by over one order of magnitude,and induce a periodic resistance oscillation due to the geometric resonance.Such nonlinear transport results from the high nonequilibrium state induced by an electrical field near the band edge.Our results suggest an insulating phase in Eu Cd_(2)As_(2)and put a strong constraint on the underlying mechanism of anomalous transport properties in this system.

Growth kinetics of titanium boride layers on the surface of Ti6Al4V

Dual titanium boride layers consisting of continuous TiB2 top-layer and TiB whisker sub- layer were formed on the surface of Ti6Al4V alloy using powder-pack boriding technique. An iso-thickness diagram of the whole boride layer was fitted with the data of thickness of the coating, treatment time and process temperature using Sigma Plot10.0 software. Growth kinetics of the titanium boride layer were analyzed by measuring the extent of penetration of TiB2 and TiB whisker as a function of boriding time in the range of 5-20 h and boriding temperature in the range of 1000-1100 ℃. By the linear regression analysis of growth kinetics of titanium boride layer, the diffusivity K and average diffusion activation energy （Q） of boron atoms in Ti6Al4V alloy were calculated, respectively.

Sonodynamic therapy with immune modulatable two-dimensional coordination nanosheets for enhanced anti-tumor immunotherapy

Ultrasound with deep penetration depth and high security could be adopted in sonodynamic therapy(SDT)by activating sonosensitizers to generate cytotoxic reactive oxygen species(ROS).Herein,two-dimensional(2D)coordination nanosheets composed of Zn^(2+)and Tetrakis(4-carboxyphenyl)porphyrin(TCPP)are fabricated.While exhibiting greatly enhanced ultrasoundtriggered ROS generation useful for noninvasive SDT,such Zn-TCPP 2D nanosheets show high loading capacity of oligodeoxynudeotides such as cytosine—phosphorothioate-guanine(CpG),which is a potent toll like receptor 9(TLR9)agonist useful in activating immune responses.Highly effective SD T of primary tumors could release tumor-associated antigens,which working together with Zn-TCPP/CpG adjuvant nanosheets could function like whole-tumor-cell vaccines and trigger tumor-specific immune responses.Interestingly,ultrasound itself could strengthen anti-tumor immune responses by improving the tumor-infiltration of T cells and limiting regulatory T cells in the tumor microenvironment.Thus,SDT using Zn-TCPP/CpG nanosheets after destruction of primary tumors could induce potent antitumor immune responses to inhibit distant abscopal tumors without direct SD T treatment.Moreover,SDT with Zn-TCPP/CpG could trigger strong immunological memory effects to inhibit cancer recurrence after elimination of primary tumors.Therefore,the 2D coordination nanosheet may be a promising platform to deliver potent SDT-triggered immunotherapy for highly effective cancer treatment.

A Reducing Iteration Orthogonal Matching Pursuit Algorithm for Compressive Sensing

In recent years, Compressed Sensing（CS） has been a hot research topic. It has a wide range of applications, such as image processing and speech signal processing owing to its characteristic of removing redundant information by reducing the sampling rate. The disadvantage of CS is that the number of iterations in a greedy algorithm such as Orthogonal Matching Pursuit（OMP） is fixed, thus limiting reconstruction precision.Therefore, in this study, we present a novel Reducing Iteration Orthogonal Matching Pursuit（RIOMP） algorithm that calculates the correlation of the residual value and measurement matrix to reduce the number of iterations.The conditions for successful signal reconstruction are derived on the basis of detailed mathematical analyses.When compared with the OMP algorithm, the RIOMP algorithm has a smaller reconstruction error. Moreover, the proposed algorithm can accurately reconstruct signals in a shorter running time.

Magnetic field-induced electronic phase transition in the Dirac semimetal state of black phosphorus under pressure

Different instabilities have been confirmed to exist in the three-dimensional(3D) electron gas when it is confined to the lowest Landau level in the extreme quantum limit. The recently discovered 3D topological semimetals offer a good platform to explore these phenomena due to the small sizes of their Fermi pockets, which means the quantum limit can be achieved at relatively low magnetic fields. In this work, we report the high-magnetic-field transport properties of the Dirac semimetal state in pressurized black phosphorus. Under applied hydrostatic pressure, the band structure of black phosphorus goes through an insulator-semimetal transition. In the high pressure topological semimetal phase, anomalous behaviors are observed on both magnetoresistance and Hall resistivity beyond the relatively low quantum limit field, which is demonstrated to indicate the emergence of an exotic electronic state hosting a density wave ordering. Our findings bring the first insight into the electronic interactions in black phosphorus under intense field.

超导β-W薄膜中厚度调控的普适类

本文使用磁控溅射生长了不同厚度的超导β-W薄膜.在具有不同无序强度不同厚度的β-W薄膜中观察到可调控的超导普适类(TUC),它们对应完全不同的临界行为,在面内磁场和面外磁场中均显示出显著的TUC性质.具体来说,超导金属相变的普适类会随着β-W薄膜厚度不同而变化2次:当厚度达到8 nm时,普适类将从量子格里菲斯奇异性(QGS)变到多重量子临界性;而当厚度进一步达到16 nm时,多重量子临界性将转变为单量子临界性.值得一提的是,通过有限尺度缩放方法可得到2 nm样品中具有超高的量子临界指数zv~30 (0.05 K温度下).这个数值是目前报道最高的,同时,超导金属相变在面内磁场下也被观察到,并具有相似的TUC性质.

Transport evidence of 3D topological nodal-line semimetal phase in ZrSiS

Topological nodal-line semimetal is a new emerging material, which is viewed as a three-dimensional （3D） analog of graphene with the conduction and valence bands crossing at Dirac nodes, resulting in a range of exotic transport properties. Herein, we report on the direct quantum transport evidence of the 3D topological nodal-line semimetal phase of ZrSiS with angular-dependent magnetoresistance （MR） and the combined de Hass-van Alphen （dHvA） and Shubnikov-de Hass （SdH） oscillations. Through fitting by a two-band model, the MR results demonstrate high topological nodal-line fermion densities of approximately 6 × 10^21 cm^-3 and a perfect electron/hole compensation ratio of 0.94, which is consis- tent with the semi-classical expression fitting of Hall conductance Gxy and the theoretical calculation. Both the SdH and dHvA oscillations provide clear evidence of 3D topological nodal-line semimetal characteristic.