Thickness-dependent anisotropic transport of phonons and charges in few-layered PdSe2.

So far, layered PdSe2 has attracted much attention due to its completely tunable band-gap with varying layer numbers, yet the thickness-dependent transporting properties have been rarely studied. We have systematically studied the electronic structures, phonon and charge transport properties, and thermoelectric properties of few-layered (from 1L to 4L) and bulk PdSe2 by first-principles calculations and Boltzmann transport theory. As the thickness increases, the energy levels of band edges relative to 4s of selenium move oppositely due to their different bonding states, leading to the power-law decrease of the band-gap. Meanwhile, the electron effective mass decreases rapidly while the hole effective mass increases significantly compared with those unperturbed. Calculations on elastic constants reveal that both bulk and few-layered PdSe2 are mechanically stable, and the bulk is ductile with a Poisson's ratio of 0.27. The shifts of Raman active modes with respect to the thickness as well as their Gruneisen parameters are analyzed and the underlying physics is discussed. At room temperature, the thermal conductivities of the bulk are 7.7, 10.1 and 0.9 W m-1 K-1 along the a, b and c axes, respectively. It is found that the low-frequency modes (<2.0 THz) contribute about 80% of in-plane thermal conductivities. Due to the enhanced contribution from the ZA mode, the thermal conductivity of few-layered PdSe2 is much larger than that of the bulk. The ZA mode is mainly scattered by itself and the Umklapp scattering dominates in the process as the thickness increases. Calculations on charge transport reveal that the electron mobility increases from 2.5-13.2 (1L) to 121.9-167.8 (4L) cm2 V-1 s-1 with the decreasing anisotropy µb/µa, while the hole mobility remains to be ∼20 cm2 V-1 s-1, which is in good agreement with the experimental results. Calculations on the thermoelectric properties reveal that the ZT value as well as the power factor increases largely as the thickness increases and it gets to be optimum for the triple layer. Interestingly, the transport of electrons and phonons is decoupled along the out-of-plane direction, which makes bulk PdSe2 exhibit good thermoelectric performance along the c axis.

The toxicity mechanism of toxic compounds from Euphorbiae pekinensis Radix on zebrafish embryos.

Euphorbiae pekinensis Radix (EP) is effective in treating various diseases, but it's toxicity is a major obstacle in use in clinical. Although EP was processed with vinegar to reduce it's toxicity, the detailed mechanism of toxicity in EP have not been clearly delineated. This study investigate the toxicity attenuation-mechanism of Euphorbiae pekinensis after being processed with vinegar (VEP) and the toxic mechanism of four compounds from EP on zebrafish embryos. The contents of four compounds decreased obviously in VEP. Correspondingly, slower development on embryos can be seen as some symptoms like reduction of heart rate, liver area and gastrointestinal peristalsis after exposed to the compounds. Some obvious pathological signals such as pericardial edema and yolk sac edema were observed. Furthermore, the compounds could increase the contents of MDA and GSH-PX and induce oxidative damage by inhibiting the activity of SOD. Also, four compounds could provoke apoptosis by up-regulating the expression level of p53, MDM2, Bax, Bcl-2 and activating the activity of caspase-3, caspase-9. In conclusion, the four compounds play an important role in the toxicity attenuation effects of VEP, which may be related to the apoptosis induction and oxidative damage. This would contribute to the clinical application and further toxicity-reduction mechanism research.

First-principles study on the anisotropic transport of electrons and phonons in monolayer and bulk GaTe: a comparative study.

Recently, monoclinic-phase GaTe has attracted much attention due to its potential applications in nanoelectronics. Despite the experimental research, theoretical studies on the thermal and transport properties, which are necessary to provide information for future applications, are still absent. We have systematically investigated the electronic, phonon and electron transporting, and thermoelectric properties of monolayer and bulk GaTe using first-principles calculations plus the Boltzmann transport equation. At the valence band maximum and conduction band minimum, the effective mass shows large anisotropy as the band dispersions are along different k-paths. The group velocity of acoustic modes also shows large anisotropy owing to the in-plane low-symmetry. Our calculations reveal that the in-plane thermal conductivities, κa and κb, take 3.5 and 8.9 W m-1 K-1, respectively, for the bulk at 300 K, compared to κa = 5.5 and κb = 10.4 W m-1 K-1 of the monolayer. Due to the van der Waals interactions between interlayers, the out-of-plane thermal conductivity is very small, κc = 1.8 W m-1 K-1. The difference between the in-plane thermal conductivities of the bulk and the monolayer can be attributed to the strengthened Umklapp scattering, which is caused by the stiffening of the lowest-frequency optical mode in the bulk. The hole mobilities of the bulk is found to be about 12-35 cm2 V-1 s-1 at 300 K, in good agreement with the experimental results. The monolayer is found to have smaller mobility but larger anisotropy than those of the bulk. Interestingly, the out-of-plane conductivity is anomalously larger than the in-plane one for the bulk, which is attributed to the orbital overlaps between the interlayer Te atoms. Moreover, n-type GaTe is found to have much larger mobility and anisotropy than the p-type one, which is useful for future applications. Compared with the case of monolayer GaTe, thermoelectric performance can be enhanced by one order of magnitude for the bulk GaTe by exploiting the out-of-plane thermal and electrical conductivities.

Theoretical prediction of intrinsic electron mobility of monolayer InSe: first-principles calculation.

Recently, a novel two-dimensional (2D) semiconductor, InSe, has attracted great attention due to its potential applications in optoelectronic devices and field effect transistors. In this study, phonon-limited mobility is investigated by the first-principles calculation. At 300 K, the intrinsic electron mobilities calculated from the electron-phonon coupling (EPC) matrix element are as high as [Formula: see text] (zigzag direction) and [Formula: see text] [Formula: see text] (Armchair direction), respectively. The deformation potential theory (DPT) based on longitudinal acoustic and optical phonon scattering is also employed to investigate electron mobility. The mobility from optical phonon scattering is much higher than that from longitudinal acoustic phonon scattering. If the polarization characteristics of InSe are not considered, the electron mobility calculated from EPC matrix element is closed to that from the longitudinal acoustic phonon DPT. In this study, we have also investigated the effect of polarization properties in 2D InSe on electron mobility. At 300 K, the electron mobility for including Fröhlich interaction is reduced to [Formula: see text] and [Formula: see text] [Formula: see text]. Therefore, the electron mobility for InSe is controlled by the scattering from polar phonons. The mobility can be increased to [Formula: see text] and [Formula: see text] [Formula: see text] under 4% biaxial strain. This result is compared with the experiment, and some disagreements are explained.

[Effects of Euphorbiae Pekinensis Radix before and after processing with vinegar on liver and gastrointestinal toxicity of zebrafish embryos].

To study the effects of different fraction of Euphorbiae Pekinensis Radix before and after processing with vinegar on liver and gastrointestinal toxicity of zebrafish embryos,the zebrafish embryos after fertilized 12 h(12 hpf) were exposed to different concentrations of solution until 96 h(96 hpf),for observation of the toxicity response of the liver and gastrointestinal of individual zebrafish embryos. The results showed that toxicity increased in a dose-dependent manner. The liver and gastrointestinal toxicity of the zebrafish embryos in various polar fractions of Euphorbiae Pekinensis Radix before and after processing with vinegar was mainly manifested as slow liver development,smaller liver area,edema of yolk sac,delayed absorption,slowing of gastrointestinal motility,abnormal function of gastrointestinal goblet cell secretion. In addition,the toxicity of different polarity was followed by petroleum ether,dichloromethane,ethyl acetate. The above results indicated that the toxicity was reduced after processing with vinegar,and the fractions of petroleum ether and methylene chloride were the main sites responsible for liver and gastrointestinal toxicity.

Realizing both giant magnetic anisotropy and quantum anomalous Hall effect in graphene with adsorbed Te-Co dimer.

To realize quantum anomalous Hall state at higher temperature, it needs to search for the magnetic topological insulators with giant magnetic anisotropy. We have studied the structural, magnetic and topological properties of graphene with adsorbed Te-A (A [Formula: see text] Co, Rh, Ir) dimers by first-principles calculations and Wannier technique. Our results reveal that the system of Te-Co@G is an excellent magnetic topological insulator with both perpendicular magnetic anisotropy of 61.7 meV and large topological band-gap of 35.8 meV. Both the magnetic anisotropy and the band-gap can be effectively tuned by the applied electric field. The dimers are stably adsorbed onto the graphene and the systems are robust against thermal fluctuation. Topological analysis reveals that the adsorption system is the Chern insulator with [Formula: see text].

Protecting quantum anomalous Hall state from thermal fluctuation via the giant magnetic anisotropy of Os-based dimers.

To protect the quantum anomalous Hall state from thermal fluctuation, it is necessary to search for magnetic topological insulators with giant magnetic anisotropy. We have investigated the magnetic and topological properties of Os-based dimers adsorbed onto graphene by density-functional calculations plus the Wannier-function technique. Our results reveal that the systems of Os-Fe@G, Os-Ru@G, and Os-Rh@G possess both giant magnetic anisotropy, typically larger than 100 meV, and a large nontrivial topological band gap. Both the magnetic anisotropy and the band gap can be effectively tuned by the electric field. The dimers prefer ferromagnetic coupling and are stable against thermal fluctuation. The topological band-gap opening can be attributed to the intrinsic spin-orbital coupling of the dimer rather than Rashba spin-orbital coupling. These Chern insulators are found to be [script C] = ±2 with two conducting edge states crossing the Fermi level.

Simultaneous quantification of twelve compounds in ethyl acetate extracts of Euphorbia kansui before and after fry-baked with vinegar by UPLC-MS/MS and its toxic effect on zebrafish.

The dried roots of Euphorbia kansui T.N. Liou ex T.P. Wang have been traditionally used for edema in China. However, the severe toxicity caused by Euphorbia kansui has seriously restricted its clinical application. Therefore, in order to study the material basis of the toxicity attenuation effect of processing with vinegar, a rapid, sensitive, validated and reliable UPLC-MS/MS method was developed to determine twelve compounds in ethyl acetate extracts of Euphorbia kansui before and after fry-baked with vinegar simultaneously. Meanwhile, the study of their toxic effect on zebrafish was conducted. Chromatographic separation was accomplished on Waters BEH C18 UPLC column. 0.3% formic acid in water and acetonitrile were used as mobile phase with a flow rate of 0.40 mL/min and a temperature at 30 °C. The analysis was performed in multiple reaction monitoring (MRM) mode using positive electrospray ionization (ESI). Furthermore, the toxic research results indicated that the toxicity of Euphorbia kansui was decreased after vinegar-processed, which might because of the increase in the content of 5-O-benzoyl-20-deoxyingenol and the decrease in the contents of the remaining terpenoids in ethyl acetate extracts of Euphorbia kansui fry-baked with vinegar. This study demonstrated that the method used is a powerful approach to determine the content of twelve compounds that responsible for the toxic effect of Euphorbia kansui at the same instant. And provided the experimental evidence for the rationale behind the reduction of toxicity.

Giant magnetic anisotropy and robust quantum anomalous Hall effect in boron-doped graphene with Re-adsorption.

Recently topological materials have attracted much attention due to their quantization transports as well as edge states. It will be excellent to realize the robust quantum anomalous Hall transports in graphene-based devices. Using density-functional theory and tight-binding method, we investigated the structural, magnetic and topological properties for the boron-doped graphene with Re-adsorption. A large band-gap of 32.5 meV is opened by the Rashba spin-orbital coupling, and the band-gap is robust against the shape deformation of ±[Formula: see text] along the zigzag direction. Giant magnetic anisotropy emerges in this adsorption system together with the Fermi level lying in the band gap. Both the magnetic anisotropy and the band gap can be tuned by a moderate electric field. Calculations reveal that the system exhibits the quantization transports with the Chern number [Formula: see text].

Anti-thrombotic and pro-angiogenic effects of Rubia cordifolia extract in zebrafish.

ETHNOPHARMACOLOGICAL RELEVANCE: Rubia cordifolia is a common traditional Chinese medicine that promotes blood circulation and eliminates blood stasis, and has been used to cure diseases related to blood stasis syndrome (BSS) clinically for many years. It has been previously demonstrated that anti-thrombosis and pro-angiogenesis can improve BSS. However, the anti-thrombotic and pro-angiogenic activities of Rubia cordifolia have not been well investigated. AIM OF STUDY: To determine the potential anti-thrombotic and pro-angiogenic activities of Rubia cordifolia and to elucidate the underlying mechanisms. In addition, the major chemical constituents of Rubia cordifolia extract (QC) were qualitatively analysed by UPLC-Q-TOF/MS to explore the association between pharmacological activity and chemical constituents. MATERIAL AND METHODS: The QC samples were composed of a 95% ethanol extract and an aqueous extract following extraction using 95% ethanol. UPLC-Q-TOF/MS was used to analyse the major chemical constituents of QC. For the anti-thrombotic experiment of QC, a phenylhydrazine (PHZ)-induced AB strain zebrafish thrombosis model was used. The zebrafish larvae were stained using O-dianisidine, and the heart and caudal vein of the zebrafish were observed and imaged with a fluorescence microscope. The staining intensity of erythrocytes in the heart (SI) of each group and the morphology of thrombus in the caudal vein were used to assess the anti-thrombotic effect of QC. For the pro-angiogenic assay of QC, the intersegmental blood vessel (ISV) insufficiency model of Tg(fli-1: EGFP)y1 transgenic zebrafish (Flik zebrafish), which was induced by the VEGF receptor tyrosine kinase inhibitor II (VRI), was used. The morphology of the intact ISVs and defective ISVs was observed to evaluate the pro-angiogenic activity of QC. The mechanism involved in promoting angiogenesis was studied with real-time PCR. RESULTS: A total of 12 components in QC were identified based on standard compounds and references, including nine anthraquinones and three naphthoquinones. After treatment with QC, the PHZ-induced thrombosis in AB strain zebrafish larvae decreased to a certain degree, which we believe was related to its dosages, and the therapeutic effect within the 50-200 µg/mL QC treatment groups was especially prominent (P < 0.01, P < 0.001) compared to that in the PHZ model group. Similarly, QC also recovered the loss of the ISVs, which was induced by VRI in Flik zebrafish larvae, which have a certain dose-effect relationship. The pro-angiogenic activity of QC was also conspicuous (P < 0.01, P < 0.001) compared to that of the VRI model group. The following real-time PCR assay proved that QC significantly restored the VRI-induced downregulation of vWF, VEGF-A, kdrl, and flt-1 in Flik zebrafish (P < 0.05, P < 0.01, P < 0.001). CONCLUSIONS: A total of 12 compounds from QC were analysed by UPLC-Q-TOF/MS. The data of the pharmacological experiments demonstrated that QC presented anti-thrombotic and pro-angiogenic activities in zebrafish, and the principal active components were likely anthraquinones and naphthoquinones. Thus, the current study provided a theoretical basis for the clinical use of Rubia cordifolia as a traditional Chinese medicine in promoting blood circulation and eliminating stasis.

Diblock Copolymer PF-b-PDMAEMA as Effective Cathode Interfacial Material in Polymer Solar Cells.

An alcohol-soluble diblock copolymer poly[2,7-(9,9-dihexylfluorene)]15-block-poly[2-(dimethylamino)ethyl methacrylate]75 (denoted as PF15-b-PDMAEMA75) was employed as the cathode interfacial layer (CIL) in p-i-n polymer solar cells (PSCs). PF15-b-PDMAEMA75 contains a conjugated rigid block and a nonconjugated flexible block grafted with polar amino groups, and it can effectively lower the work function of the Al cathode and decrease the series resistance of the devices. When applied as the CIL in PSCs based on poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexy)carbonyl]thieno[3,4-b]thiophenediyl]]:[6,6]-phenyl C71 butyric acid methyl ester, the champion power conversion efficiency of 8.80% was achieved, which is slightly higher than that of the PSCs using the well-known poly[(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] as CIL under our experimental conditions, and much better than that of PSCs using Ca as CIL. The improvement of the performance is mainly attributed to the enhanced open-circuit voltage and fill factor. To the best of our knowledge, this is the first time a diblock copolymer has been used as a CIL in PSCs, and this study may provide a novel avenue for the design and synthesis of interfacial materials for high-performance PSCs.

[Acute toxicity of Euphorbiae Pekinensis Radix and vinegar-processing Euphorbiae Pekinensis Radix on zebrafish embryo].

The embryos of model organism zebrafish were used to evaluate the acute toxicity of the extracts of Euphorbiae Pekinensis Radix and vinegar-processing Euphorbiae Pekinensis Radix, and the total terpene content of each extract was determined by using euphol as the reference standards. Twenty-four h normally developed zebrafish embryos were chosen, and 8 concentrations were adopted for each extract. Then the growth and death of zebrafish embryos were observed at 96 h after administration, and median lethal concentrations (LC50) of the different samples on zebrafish embryos were calculated. The results showed that all of the extracts (before and after vinegar processing) had acute toxicity on zebrafish embryos. The toxicity of vinegar-processing Euphorbiae Pekinensis Radix was significantly lower than that of crude Euphorbiae Pekinensis Radix. Among different extraction methods, ethanol extract was more poisonous than water extract; in different polarity fractions, the toxicity was in the following order: petroleum ether>dichloromethane>ethyl acetate>n-butyl alcohol and remaining part. Combined with the results of the determination of terpene components, it can be concluded that the terpenoids are the main toxic components of Euphorbiae Pekinensis Radix, positively correlated with toxicity degree. It indicates that the zebrafish embryo model is appropriate for the toxicity evaluation of Euphorbiae Pekinensis Radix and provides appropriate research methods and theoretical basis for the further study of the toxic components and the mechanism of reducing toxicity.

Comprehensive Study of Sol-Gel versus Hydrolysis-Condensation Methods To Prepare ZnO Films: Electron Transport Layers in Perovskite Solar Cells.

Owing to the high charge mobility and low processing temperature, ZnO is regarded as an ideal candidate for electron transport layer (ETL) material in thin-film solar cells. For the film preparation, the presently dominated sol-gel (SG) and hydrolysis-condensation (HC) methods show great potential; however, the effect of these two methods on the performance of the resulting devices has not been investigated in the same frame. In this study, the ZnO films made through SG and HC methods were applied in perovskite solar cells (Pero-SCs), and the performances of corresponding devices were compared under parallel conditions. We found that the surface morphologies and the conductivities of the films prepared by SG and HC methods showed great differences. The HC-ZnO films with higher conductivity led to relatively higher device performance, and the best power conversion efficiencie (PCE) of 12.9% was obtained; meanwhile, for Pero-SCs based on SG-ZnO, the best PCE achieved was 10.9%. The better device performance of Pero-SCs based on HC-ZnO should be attributed to the better charge extraction and transportation ability of HC-ZnO film. Moreover, to further enhance the performance of Pero-SCs, a thin layer of pristine C60 was introduced between HC-ZnO and perovskite layers. By doing so, the quality of perovskite films was improved, and the PCE was elevated to 14.1%. The preparation of HC-ZnO film involves relatively lower-temperature (maximum 100 °C) processing; the films showed better charge extraction and transportation properties and can be a more promising ETL material in Pero-SCs.

Giant magnetic anisotropy of rare-earth adatoms and dimers adsorbed by graphene oxide.

Nowadays, transition-metal adatoms and dimers with giant magnetic anisotropy have attracted much attention due to their potential applications in data storage, spintronics and quantum computations. Using density-functional calculations, we investigated the magnetic anisotropy of the rare-earth adatoms and dimers adsorbed by graphene oxide. Our calculations reveal that the adatoms of Tm, Er and Sm possess giant magnetic anisotropy, typically larger than 40 meV. When the dimers of (Tm,Er,Sm)-Ir are adsorbed onto graphene oxide, the magnetic anisotropy even exceeds 200 meV. The magnetic anisotropy can be tuned by the external electric field as well as the environment.

Ultrabroad Photoluminescence and Electroluminescence at New Wavelengths from Doped Organometal Halide Perovskites.

Doping of semiconductors by introducing foreign atoms enables their widespread applications in microelectronics and optoelectronics. We show that this strategy can be applied to direct bandgap lead-halide perovskites, leading to the realization of ultrawide photoluminescence (PL) at new wavelengths enabled by doping bismuth (Bi) into lead-halide perovskites. Structural and photophysical characterization reveals that the PL stems from one class of Bi doping-induced optically active center, which is attributed to distorted [PbI6] units coupled with spatially localized bipolarons. Additionally, we find that compositional engineering of these semiconductors can be employed as an additional way to rationally tune the PL properties of doped perovskites. Finally, we accomplished the electroluminescence at cryogenic temperatures by using this system as an emissive layer, marking the first electrically driven devices using Bi-doped photonic materials. Our results suggest that low-cost, earth-abundant, solution-processable Bi-doped perovskite semiconductors could be promising candidate materials for developing optical sources operating at new wavelengths.

Thermoelectric effect in an Aharonov-Bohm ring with an embedded quantum dot.

Thermoelectric effect is studied in an Aharonov-Bohm interferometer with an embedded quantum dot (QD) in the Coulomb blockade regime. The electrical conductance, electron thermal conductance, thermopower, and thermoelectric figure-of-merit are calculated by using the Keldysh Green's function method. It is found that the figure-of-merit ZT of the QD ring may be quite high due to the Fano effect originated from the quantum interference effect. Moreover, the thermoelectric efficiency is sensitive to the magnitude of the dot-lead and inter-lead coupling strengthes. The effect of intradot Coulomb repulsion on ZT is significant in the weak-coupling regime, and then large ZT values can be obtained at rather high temperature.

Quantum interference effect in electron tunneling through a quantum-dot-ring spin valve.

Spin-dependent transport through a quantum-dot (QD) ring coupled to ferromagnetic leads with noncollinear magnetizations is studied theoretically. Tunneling current, current spin polarization and tunnel magnetoresistance (TMR) as functions of the bias voltage and the direct coupling strength between the two leads are analyzed by the nonequilibrium Green's function technique. It is shown that the magnitudes of these quantities are sensitive to the relative angle between the leads' magnetic moments and the quantum interference effect originated from the inter-lead coupling. We pay particular attention on the Coulomb blockade regime and find the relative current magnitudes of different magnetization angles can be reversed by tuning the inter-lead coupling strength, resulting in sign change of the TMR. For large enough inter-lead coupling strength, the current spin polarizations for parallel and antiparallel magnetic configurations will approach to unit and zero, respectively.PACS numbers:

Low molecular weight heparin in the treatment of severe acute pancreatitis: a multiple centre prospective clinical study.

OBJECTIVE: To study the effect of low molecular weight heparin (LMWH) in the treatment of severe acute pancreatitis (SAP). METHODS: A total of 265 SAP patients were randomly divided into two groups: firstly, the conventional treatment group (C group, n = 130; and secondly the conventional treatment plus the LMWH treatment group (LT group, n = 135). The clinical parameters, laboratory parameters and computed tomography (CT) score of pancreatic necrosis (CTSPN) in the two groups were compared. RESULTS: On admission, all the clinical parameters, laboratory parameters and CTSPN in the two groups were not significantly different (p > 0.05). However, after treatment, in LT group, the clinical presentation improvement rate and laboratory parameters improvement were significantly higher than those in C group (p < 0.05-0.01), and the acute physiology and chronic health evaluation (APACHE) II score, complication rate, mortality and mean hospital stay in LT group were obviously lower than those in C group (p < 0.05-0.01). The CT score in LT group was much lower than that in C group (p < 0.05). Two weeks after treatment FBI decreased obviously in C group, but not in LT group, and no haemorrhagic complications occurred. CONCLUSIONS: LMWH can enhance the effect of conventional treatment for SAP, and can markedly decrease the mortality of SAP. LMWH is a simple, safe, economic and effective method for treatment of SAP. It is can be used in every hospital.

[1,1'-Bis(diphenyl-phosphino)cobalto-cenium-κP,P']dichloridoplatinum(II) hexa-fluorido-phosphate.

The title bimetallic compound, [PtCl(2){Co(C(17)H(14)P)(2)}]PF(6), was obtained by reaction of 1,1'-bis-(diphenyl-phosphino)cobalto-cenium hexa-fluorido-phosphate with bis-(acetonitrile)di-chloridoplatinum. The Pt(II) ion is four-coordinated in a slightly distorted square-planar environment by two P atoms of the 1,1'-bis-(diphenyl-phosphino)cobaltocenium moiety and two Cl atoms. In the crystal structure, mol-ecules are linked by weak C-H⋯F and C-H⋯Cl hydrogen bonds.

[Determination of trace elements in waste beer yeasts by ICP-MS with microwave digestion].

The waste beer yeast has rich nutritional compositions and is widely used in food, medical and forage industries. The security of the yeast plays an important role in everyone's daily life. But the yeast contanining microamount of lead, cadmium, chromium, arsenic and other harmful metals is endangering human health. A new method was developed for the direct determination of eight elements, namely copper, lead, zinc, iron, manganese, cadmium, chromium and arsenic in waste beer yeast by inductively coupled plasma-mass spectrometry (ICP-MS) with microwave digestion. The parameters of plasma system, mass system, vacuum system and spectrometer system were optimized. The spectral interferences were eliminated by selecting alternation analytical isotopes of 65Cu, 208Pb, 66Zn, 57Fe, 55Mn, 114Cd, 52Cr and 5As, and the internal standards of Rh was selected to compensate the drift of analytical signals. The samples were digested with concentrated nitric acid-hydrogen peroxide (2:1) mixed solution more rapidly and more effectively. The effects of the type of mixed acid , the volume of digesting solution, heating time, and heating power were investigated in detail. In the closed system, the complete digestion was performed using 4 mL HNO3 and 2mL H2O2 for 2.0 min at 0.5 MPa, 3 min at 1.0 MPa and 5 min at 1.5 MPa. The detection limits of these eight elements were 0.013-0.122 microg x L(-1). The relative standard deviation (RSD) was 0.94%-3.26% (n=9), and the addition standard recovery was 98.4%-102.6% for all elements. The proposed method has been applied to the determination of trace elements of Cu, Pb, Zn, Fe, Mn, Cd, Cr and As in waste beer yeast samples with satisfactory results. The determination results indicated that the content of trace elements of Cu, Pb, Cd and As in waste beer yeast samples are significantly low.