Deriving atmospheric parameters of a large sample of stars is of vital importance to understand the formation and evolution of the Milky Way.Photometric surveys,especially those with near-ultraviolet filters,can offer...Deriving atmospheric parameters of a large sample of stars is of vital importance to understand the formation and evolution of the Milky Way.Photometric surveys,especially those with near-ultraviolet filters,can offer accurate measurements of stellar parameters,with the precision comparable to that from low/medium resolution spectroscopy.In this study,we explore the capability of measuring stellar atmospheric parameters from Chinese Space Station Telescope(CSST)broad-band photometry(particularly in the near-ultraviolet bands),based on synthetic colors derived from model spectra.We find that colors from the optical and near-ultraviolet filter systems adopted by CSST show significant sensitivities to the stellar atmospheric parameters,especially the metallicity.According to our mock data tests,the precision of the photometric metallicity is quite high,with typical values of0.17 and 0.20 dex for dwarf and giant stars,respectively.The precision of the effective temperature estimated from broad-band colors are within 50 K.展开更多
Drug discovery is a crucial part of human healthcare and has dramatically benefited human lifespan and life quality in recent centuries, however, it is usually time-and effort-consuming. Structural biology has been de...Drug discovery is a crucial part of human healthcare and has dramatically benefited human lifespan and life quality in recent centuries, however, it is usually time-and effort-consuming. Structural biology has been demonstrated as a powerful tool to accelerate drug development. Among different techniques, cryo-electron microscopy(cryo-EM) is emerging as the mainstream of structure determination of biomacromolecules in the past decade and has received increasing attention from the pharmaceutical industry. Although cryo-EM still has limitations in resolution, speed and throughput, a growing number of innovative drugs are being developed with the help of cryo-EM. Here, we aim to provide an overview of how cryo-EM techniques are applied to facilitate drug discovery. The development and typical workflow of cryo-EM technique will be briefly introduced, followed by its specific applications in structure-based drug design, fragment-based drug discovery, proteolysis targeting chimeras, antibody drug development and drug repurposing. Besides cryo-EM, drug discovery innovation usually involves other state-of-the-art techniques such as artificial intelligence(AI), which is increasingly active in diverse areas. The combination of cryo-EM and AI provides an opportunity to minimize limitations of cryo-EM such as automation, throughput and interpretation of mediumresolution maps, and tends to be the new direction of future development of cryo-EM. The rapid development of cryo-EM will make it as an indispensable part of modern drug discovery.展开更多
Background Growth-differentiation factor-15(GDF-15)is a promising prognostic biomarker in patients with chronic heart failure (CHF).Comparatively little is known about the value of repeated measurement of GDF-15with C...Background Growth-differentiation factor-15(GDF-15)is a promising prognostic biomarker in patients with chronic heart failure (CHF).Comparatively little is known about the value of repeated measurement of GDF-15with CI-IF in Chinese Han population.This study sought to identify the clinical value of repeated measurement of GDF-15in Chinese Han patients with post-myocardial infarction CHF. Methods In total,232consecutive Chinese Hart patients with post-myocardial infarction CHF were enrolled prospectively from January 2014to June 2016.The plasma concentration of GDF-15was determined on admission and over 12months.Patients were followed up for all-cause death and a composite outcome of major adverse cardiac events (MACE)included all-cause death,myocardial infarction and first heart failure (HF)re-hospitalization.Association with other clinical variables and adverse outcomes of repeated measurement of GDF-15 was explored.Results The median baseline GDF-15level was 2025ng/L.Baseline GDF-15was moderately associated with baseline N-terminal pro-B type nalriuretic peptide (NT-proBNP)(coefficient 0.561,P <0.001).During a median follow-up of 20months,there were 53deaths and 100MACE.GDF-I5remained an independent predictor of all-cause death (adjusted hazard ratio 1.826per 1Ln U,95%CI: 1.037-8.360;P =0.037)and MACE (adjusted hazard ratio 2.243per I Ln U,95%CI:1.181-1.775;P <0.001)adjusted for established risk factors.Repeated measurement of GDF-15was performed in 173survivals over 12months.Increase of GDF-15over 12months was associ- ated with dilatation of left ventricle and acted as an independent predictor of subsequent all-canse death (adjusted HR =3.164,95%CI: 1.245~.041;P =0.015).In the joint model,GDF-15was also shown to be a risk factor for all-cause death (HR =2.749,95%CI: 1.667-3.831;P <0.001)and MACE (FIR =2.434,95%CI:1.425-3.443;P <0.001).Conclusions Repeated measurements of GDF-15 have promising prognostic value of the risk of all-cause death in Chinese Han patients with CI-IF post-myocardial infarction.GDF-15may influence the post-myocardial infarction CI-IF through the path physiological pathway of myocardial remodeling.展开更多
AIM:To evaluate the role of probiotics in the standard triple Helicobacter pylori therapy.METHODS:In this meta-analysis,we investigated the efficacy of probiotics in a standard triple H.pylori therapy in adults.Search...AIM:To evaluate the role of probiotics in the standard triple Helicobacter pylori therapy.METHODS:In this meta-analysis,we investigated the efficacy of probiotics in a standard triple H.pylori therapy in adults.Searches were mainly conducted in MEDLINE/Pub Med,EMBASE,and the Cochrane Central Register of Controlled Trials.Fourteen studies met our criteria,and the quality of these studies was assessedusing the Jadad scale.We used STATA version 12.0to extract data and to calculate the odds ratios(ORs),which are presented with the corresponding 95%confidence intervals(CIs).The data are presented as forest plots.RESULTS:The pooled ORs for the eradication rates calculated by intention-to-treat analysis and perprotocol analysis in the probiotic group vs the control group were 1.67(95%CI:1.38-2.02)and 1.68(95%CI:1.35-2.08),respectively,using the fixed-effects model.The sensitivity of the Asian studies was greater than that of the Caucasian studies(Asian:OR=1.78,95%CI:1.40-2.26;Caucasian:OR=1.48,95%CI:1.06-2.05).The pooled OR for the incidence of total adverse effects was significantly lower in the probiotic group(OR=0.49,95%CI:0.26-0.94),using the random effects model,with significant heterogeneity(I2=85.7%).The incidence of diarrhea was significantly reduced in the probiotic group(OR=0.21,95%CI:0.06-0.74),whereas the incidence of taste disorders,metallic taste,vomiting,nausea,and epigastric pain did not differ significantly between the probiotic group and the control group.CONCLUSION:Supplementary probiotic preparations during standard triple H.pylori therapy may improve the eradication rate,particularly in Asian patients,and the incidence of total adverse effects.展开更多
This paper summarizes melting methods of titanium and titanium alloy, such as vacuum arc melting(VAR) and electron beam cold hearth melting(EBCHM), and the related inclusions formed when using these melting methods. L...This paper summarizes melting methods of titanium and titanium alloy, such as vacuum arc melting(VAR) and electron beam cold hearth melting(EBCHM), and the related inclusions formed when using these melting methods. Low-density inclusions are resulted from contamination of air, and high-density inclusions are caused by refractory elements. The formation process of inclusions was analysed. The removal mechanism of different kinds of inclusions was specified. Low-density inclusions are removed mainly by resolving. This is a comprehensive process containing reaction diffusion. The resolving rate of high-density inclusions is so low that these inclusions are mainly removed by sedimentation. The experiments and physical models of inclusions are detailed. In various melting methods, vacuum arc melting is prominent. However, this method cannot remove inclusions effectively, which usually results in repeat melting. Electron beam cold hearth melting has the best ability of removing inclusions. These results can provide instructions to researchers of titanium and titanium alloys.展开更多
The infl uence of Si, Sn, Mo and Ni on the ductility and thermal conductivity of compacted graphite iron(CGI) was investigated. Metallographic observation and Differential Scanning Calorimetry(DSC) experiments were ca...The infl uence of Si, Sn, Mo and Ni on the ductility and thermal conductivity of compacted graphite iron(CGI) was investigated. Metallographic observation and Differential Scanning Calorimetry(DSC) experiments were carried out to analyze the roles of various additions in the eutectoid reaction. The experimental results showed that the ductility of CGI is proportional to the ferrite fraction, so moderate Si content could dramatically improve the ductility by increasing the ferrite fraction. DSC measurements showed that Mo has moderate inhibition on eutectoid transformation during both the heating and cooling processes, while the sample without Sn obviously broadens the three-phase region. Vermicularity and ferrite are known to improve thermal conductivity, and the former plays a more important role. Besides, among the alloy elements investigated, Sn has the greatest negative effect on conductivity, followed by Ni and Mo having the smallest effects.展开更多
As an excellent giant-magnetostrictive material, Tb-Dy-Fe alloys(based on Tb0.27-0.30Dy0.73-0.70Fe1.9-2Laves compound) can be applied in many engineering fields, such as sonar transducer systems, sensors, and micro-ac...As an excellent giant-magnetostrictive material, Tb-Dy-Fe alloys(based on Tb0.27-0.30Dy0.73-0.70Fe1.9-2Laves compound) can be applied in many engineering fields, such as sonar transducer systems, sensors, and micro-actuators. However, the cost of the rare earth elements Tb and Dy is too high to be widely applied for the materials. Nowadays, there are two different ways to substitute for these alloying elements. One is to partially replace Tb or Dy by cheaper rare earth elements, such as Pr, Nd, Sm and Ho; and the other is to use non-rare earth elements, such as Co, Al, Mn, Si, Ce, B, Be and C, to substitute Fe to form single MgCu_2-type Laves phase and a certain amount of Re-rich phase, which can reduce the brittleness and improve the corrosion resistance of the alloy. This paper systemically introduces the development, the fabrication methods and the corresponding preferred growth directions of Tb-Dy-Fe alloys. In addition, the effects of alloying elements and heat treatment on magnetostrictive and mechanical properties of Tb-Dy-Fe alloys are also reviewed, respectively. Finally, some possible applications of Tb-Dy-Fe alloys are presented.展开更多
High-temperature mechanical properties of high-boron austenitic steels(HBASs) were studied at 850 °C using a dynamic thermal-mechanical simulation testing machine. In addition, the thermal fatigue properties of t...High-temperature mechanical properties of high-boron austenitic steels(HBASs) were studied at 850 °C using a dynamic thermal-mechanical simulation testing machine. In addition, the thermal fatigue properties of the alloys were investigated using the self-restraint Uddeholm thermal fatigue test, during which the alloy specimens were cycled between room temperature and 800°C. Stereomicroscopy and scanning electron microscopy were used to study the surface cracks and cross-sectional microstructure of the alloy specimens after the thermal fatigue tests. The effects of carbon content on the mechanical properties at room temperature and high-temperature as well as thermal fatigue properties of the HBASs were also studied. The experimental results show that increasing carbon content induces changes in the microstructure and mechanical properties of the HBASs. The boride phase within the HBAS matrix exhibits a round and smooth morphology, and they are distributed in a discrete manner. The hardness of the alloys increases from 239(0.19 wt.% C) to 302(0.29 wt.% C) and 312 HV(0.37 wt.% C); the tensile yield strength at 850 °C increases from 165.1 to 190.3 and 197.1 MPa; and the compressive yield strength increases from 166.1 to 167.9 and 184.4 MPa. The results of the thermal fatigue tests(performed for 300 cycles from room temperature to 800 °C) indicate that the degree of thermal fatigue of the HBAS with 0.29 wt.% C(rating of 2–3) is superior to those of the alloys with 0.19 wt.%(rating of 4–5) and 0.37 wt.%(rating of 3–4) carbon. The main cause of this difference is the ready precipitation of M23(C,B)6-type borocarbides in the alloys with high carbon content during thermal fatigue testing. The precipitation and aggregation of borocarbide particles at the grain boundaries result in the deterioration of the thermal fatigue properties of the alloys.展开更多
The Large sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST) general survey is a spectroscopic survey that will eventually cover approximately half of the celestial sphere and collect 10 million spectra of ...The Large sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST) general survey is a spectroscopic survey that will eventually cover approximately half of the celestial sphere and collect 10 million spectra of stars, galaxies and QSOs. Objects in both the pilot survey and the first year regular survey are included in the LAMOST DR1. The pilot survey started in October 2011 and ended in June 2012, and the data have been released to the public as the LAMOST Pilot Data Release in August 2012. The regular survey started in September 2012, and completed its first year of operation in June 2013. The LAMOST DR1 includes a total of 1202 plates containing 2 955 336 spectra, of which 1 790 879 spectra have observed signalto-noise ratio(SNR) ≥ 10. All data with SNR ≥ 2 are formally released as LAMOST DR1 under the LAMOST data policy. This data release contains a total of 2 204 696 spectra, of which 1 944 329 are stellar spectra, 12 082 are galaxy spectra and 5017 are quasars. The DR1 not only includes spectra, but also three stellar catalogs with measured parameters: late A,FGK-type stars with high quality spectra(1 061 918 entries), A-type stars(100 073 entries), and M-type stars(121 522 entries). This paper introduces the survey design, the observational and instrumental limitations, data reduction and analysis, and some caveats. A description of the FITS structure of spectral files and parameter catalogs is also provided.展开更多
Fe83Ga17 alloy is a kind of promising magnetostrictive alloys with high magnetostrictive properties and a low saturation magnetic field.As-cast Fe83Ga17 Dyx(x=0,0.05,0.1,0.2,0.4)polycrystalline alloys were prepared by...Fe83Ga17 alloy is a kind of promising magnetostrictive alloys with high magnetostrictive properties and a low saturation magnetic field.As-cast Fe83Ga17 Dyx(x=0,0.05,0.1,0.2,0.4)polycrystalline alloys were prepared by arc melting.Effect of Dy doping on the microstructure,magnetostrictive and mechanical properties of as-cast Fe83Ga17 alloy was investigated.Results show that Dy-doped alloys exhibit a dual-phase structure containing the A2 matrix and Dy-rich precipitates(Fe56Ga34Dy10).Both magnetostriction and mechanical properties of Fe83Ga17 alloys are improved by Dy doping.A small amount of Dy addition(x=0.2)significantly causes Fe83Ga17 alloy to transform from typical brittle material(fracture strainε<1%)to plastic material(ε≈11%).Correspondingly,the fracture mode transforms from intergranular fracture to dimple fracture.At the same time,the ultimate tensile strength and the magnetostriction rise up to 209 MPa and 64 ppm,respectively.Dy-rich precipitates disperse along the grain boundries and inside the grains,which plays an important role in the grain refinement and solution strengthening,and therefore,contribute to the enhancement of mechanical properties of the alloy.The improvement of magnetostriction could be attributed to the large lattice distortion induced by Dy atoms entering into the A2 matrix.Doping Dy into Fe-Ga alloys provides an effective solution to the brittleness in their applications.展开更多
Planetary nebulae (PNe) are good tracers of the stellar populations, chemical composition and dynamics of their host galaxies. This paper reports the discovery of new PNe in the outskirts of the Andromeda Galaxy (...Planetary nebulae (PNe) are good tracers of the stellar populations, chemical composition and dynamics of their host galaxies. This paper reports the discovery of new PNe in the outskirts of the Andromeda Galaxy (M31) with the Guoshoujing Telescope (GSJT, formerly named the Large Sky Area Multi-Object Fiber Spectroscopic Telescope-LAMOST) during its early commissioning phase. In total, 36 candidates selected from SDSS photometry are confirmed in terms of their PN nature, including 17 new discoveries and another 19 previously known emission line objects. Their positions, spectra, radial velocities and m5007 magnitudes are presented. We discuss the potential for detecting more PNe in M 31 with GSJT's multi-object spectroscopy and the related applications in studies of the dynamics and chemistry of M 31 and its assemblage history.展开更多
The [α/Fe] ratios in stars are good tracers to probe the formation history of stellar populations and the chemical evolution of the Galaxy. The spectroscopic survey of LAMOST provides a good opportunity to determine ...The [α/Fe] ratios in stars are good tracers to probe the formation history of stellar populations and the chemical evolution of the Galaxy. The spectroscopic survey of LAMOST provides a good opportunity to determine [α/Fe] of millions of stars in the Galaxy. We present a method of measuring the [α/Fe]ratios from LAMOST spectra using the template-matching technique of the LSP3 pipeline. We use three test samples of stars selected from the ELODIE and MILES libraries, as well as the LEGUE survey to validate our method. Based on the test results, we conclude that our method is valid for measuring [α/Fe]from low-resolution spectra acquired by the LAMOST survey. Within the range of the stellar parameters Teff= [5000, 7500] K, log g = [1.0, 5.0] dex and [Fe/H]= [onsistent with values derived from high-resolution spectra,-1.5, +0.5] dex, our [α/Fe] measurements are c and the accuracy of our [α/Fe] measurements from LAMOST spectra is better than 0.1 dex with spectral signal-to-noise higher than 20.展开更多
In order to improve the performance of plaster molds for investment casting,a diverse content of glass fiber and polypropylene(PP)fiber was incorporated into the slurry for the preparation of a fiber-reinforced mold.T...In order to improve the performance of plaster molds for investment casting,a diverse content of glass fiber and polypropylene(PP)fiber was incorporated into the slurry for the preparation of a fiber-reinforced mold.The green and fired bending strengths,thermal expansion properties,permeability,and thermal shock resistance of the mold were examined,and the scanning electron microscope(SEM)with energy dispersive spectrometer(EDS)was applied for the observation of fracture morphology.With appropriate content,the introduction of glass fiber was proved to increase the green bending strength and fired bending strength,restrain the thermal expansion and improve the thermal shock resistance of the mold,while the polypropylene fiber added was able to raise the green bending strength and the permeability,reduce the thermal expansion and heighten the thermal shock resistance as well,though the fired bending strength would be weakened slightly.Evenly distributed fibers were capable of enhancing the mechanical properties of the matrix,but agglomerations and bundles of fibers resulting from excessive addition had a negative impact.Meanwhile,it was also manifested that micropores left by ablative polypropylene fibers could improve the permeability and reduce the thermal expansion of the mold,and the fired bending strength would be decreased slightly by the deterioration of continuous structure.Three different ratios of hybrid fiber were employed in plaster molds,which can meet altered requirement of castings.The samples modified with hybrid fiber possessed lower thermal deformation,higher air permeability,and better resistance of thermal shock,while the mechanical strength was equal to the fiber free sample or slightly increased.展开更多
We present preliminary analyses of spectra of quasar candidates in two Guoshoujing Telescope (GSJT, formerly named the Large Sky Area Multi-Object Fiber Spectroscopic Telescope - LAMOST) test fields near M 31 where ...We present preliminary analyses of spectra of quasar candidates in two Guoshoujing Telescope (GSJT, formerly named the Large Sky Area Multi-Object Fiber Spectroscopic Telescope - LAMOST) test fields near M 31 where one is close to the optical center of the disk and the other is towards the northeastern outskirts of the halo, obtained during the early stage of the GSJT commissioning in the last season of 2009. Both fields contain background low-redshift quasar candidates selected from the SDSS photometry. In total, 14 new quasars with redshifts up to 2 and i magnitudes between 16.7 and 19.2, are discovered, including 7 within the 2.5° central region of M 31. We briefly discuss the potential applications of these newly discovered bright quasars.展开更多
We present extensive spectroscopic observations of supernova remnant (SNR) S 147 collected with the Large sky Area Multi-Object fiber Spectroscopic Telescope (LAMOST). The spectra were care- fully sky-subtracted t...We present extensive spectroscopic observations of supernova remnant (SNR) S 147 collected with the Large sky Area Multi-Object fiber Spectroscopic Telescope (LAMOST). The spectra were care- fully sky-subtracted taking into account the complex filamentary structure of S 147. We have utilized all available LAMOST spectra toward S 147, including sky and stellar spectra. By measuring the prominent optical emission lines including Ha, [NII] )λ 6584 and [S n] λλ6717, 6731, we present maps of radial velocity and line intensity ratio covering the whole nebula of S 147 with unprecedented detail. The maps spatially correlate well with the complex filamentary structure of S147. For the central 2° of S147, the radial velocity varies from - 100 to 100 krn s^-1 and has peaks between - 0 and 10 km s^-1. The intensity ratios of Hα/[S n)λλ6717,6731, [Sn] λ 6717/λ 6731 and Ha/IN Hα/λ 6584 peak at about 0.77, 1.35 and 1.48, respectively, with a scatter of 0.17, 0.19 and 0.37, respectively. The intensity ratios are consistent with the literature values. However, the range of variations of line intensity ratios estimated here, which are representative of the whole nebula, is larger than previously estimated.展开更多
Directionally solidified porous copper is considered as a potential candidate in the field of microchannel heat sinks.By the Bridgman-type directional solidification method,a porous copper ingot was fabricated.Evoluti...Directionally solidified porous copper is considered as a potential candidate in the field of microchannel heat sinks.By the Bridgman-type directional solidification method,a porous copper ingot was fabricated.Evolution of the porosity,pore number density,average pore diameter and average interpore spacing at different ingot heights was investigated.The results show that with the increase of ingot height,the porosity firstly increases and then basically remains unchanged from the ignot height of 65 mm;the pore number density rapidly decreases at first,and the decreasing speed becomes slower when the ignot height higher than 85 mm;the average pore diameter increases and then remains unchanged from the ingot height of 85 mm;the average interpore spacing increases,and the increasing speed of average interpore spacing becomes slower with the increase of height to higher than 85 mm.In order to study the evolution of diameter and spatial distribution of pores,the distribution ranges of pore diameter,nearest-neighbor distance and radial cumulative pore number were analyzed.As the ingot height increases,the distribution ranges of pore diameter and nearest-neighbor distance firstly increase and then tend to be stable.There are no pore clusters and for long distance,the spatial distribution of pores is uniform at different ingot heights.Pore structure and 3D pore morphology of porous copper were observed with the help of light illumination and X-ray tomography.Pore nucleation,pore interruption,pore coalescence,diameter change of pores and lateral displacement of pores were found to exist in the pore structure.展开更多
The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) published its first data release (DR1) in 2013, which is currently the largest dataset of stellar spectra in the world. We combine the PASTEL ...The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) published its first data release (DR1) in 2013, which is currently the largest dataset of stellar spectra in the world. We combine the PASTEL catalog and SIMBAD radial velocities as a testing standard to validate stellar parameters (effec- tive temperature Tefr, surface gravity log g, metallicity [Fe/H] and radial velocity Vr) derived from DR1. Through cross-identification of the DR1 catalogs and the PASTEL catalog, we obtain a preliminary sample of 422 stars. After removal of stellar param- eter measurements from problematic spectra and applying effective temperature con- straints to the sample, we compare the stellar parameters from DR1 with those from PASTEL and SIMBAD to demonstrate that the DR1 results are reliable in restricted ranges of Tefr. We derive standard deviations of 110 K, 0.19 dex and 0.11 dex for Tell, log 9 and [Fe/H] respectively when Teff〈 8000 K, and 4.91 km s-1 for Vr when Teff 〈 10 000 K. Systematic errors are negligible except for those of Vr. In addition, metallicities in DR1 are systematically higher than those in PASTEL, in the range of PASTEL [Fe/H] 〈 -1.5.展开更多
Using a sample of over 70 000 red clump(RC) stars with 5%–10% distance accuracy selected from the LAMOST Spectroscopic Survey of the Galactic Anti-center(LSS-GAC), we study the radial and vertical gradients of th...Using a sample of over 70 000 red clump(RC) stars with 5%–10% distance accuracy selected from the LAMOST Spectroscopic Survey of the Galactic Anti-center(LSS-GAC), we study the radial and vertical gradients of the Galactic disk(s) mainly in the anti-center direction, covering a significant volume of the disk in the range of projected Galactocentric radius 7 ≤ RGC ≤ 14 kpc and height from the Galactic midplane 0 ≤ |Z | ≤ 3 kpc. Our analysis shows that both the radial and vertical metallicity gradients are negative across much of the volume of the disk that is probed, and they exhibit significant spatial variations. Near the solar circle(7 ≤ RGC ≤ 11.5 kpc), the radial gradient has a moderately steep, negative slope of-0.08 dex kpc-1near the midplane(|Z | 〈 0.1 kpc), and the slope flattens with increasing |Z |. In the outer disk(11.5 〈 RGC ≤ 14 kpc), the radial gradients have an essentially constant, much less steep slope of-0.01 dex kpc-1at all heights above the plane, suggesting that the outer disk may have experienced an evolutionary path different from that of the inner disk. The vertical gradients are found to flatten largely with increasing RGC. However, the vertical gradient of the lower disk(0 ≤ |Z | ≤ 1 kpc)is found to flatten with RGC quicker than that of the upper disk(1 〈 |Z | ≤ 3 kpc).Our results should provide strong constraints on the theory of disk formation and evolution, as well as the underlying physical processes that shape the disk(e.g. gas flows,radial migration, and internal and external perturbations).展开更多
基金the science research grants from the China Manned Space Project with No.CMS-CSST-2021-A08.Y.Hthe science research grants from the China Manned Space Project with No.CMS-CSST-2021-B05+3 种基金the NSFC for grant Nos.11903027 and11833006the NSFC for grant Nos.11973001,12090040,and 12090044the National Key R&D Program of China for grant No.2019YFA0405503.H.W.Zthe National Key R&D Program of China for grant No.2019YFA0405504。
文摘Deriving atmospheric parameters of a large sample of stars is of vital importance to understand the formation and evolution of the Milky Way.Photometric surveys,especially those with near-ultraviolet filters,can offer accurate measurements of stellar parameters,with the precision comparable to that from low/medium resolution spectroscopy.In this study,we explore the capability of measuring stellar atmospheric parameters from Chinese Space Station Telescope(CSST)broad-band photometry(particularly in the near-ultraviolet bands),based on synthetic colors derived from model spectra.We find that colors from the optical and near-ultraviolet filter systems adopted by CSST show significant sensitivities to the stellar atmospheric parameters,especially the metallicity.According to our mock data tests,the precision of the photometric metallicity is quite high,with typical values of0.17 and 0.20 dex for dwarf and giant stars,respectively.The precision of the effective temperature estimated from broad-band colors are within 50 K.
基金funded by the National Natural Science Foundation of China (NSFC, 31900046, 81972085, 82172465 and 32161133022)the Guangdong Provincial Key Laboratory of Advanced Biomaterials (2022B1212010003)+7 种基金the National Science and Technology Innovation 2030 Major Program (2022ZD0211900)the Shenzhen Key Laboratory of Computer Aided Drug Discovery (ZDSYS20201230165400001)the Chinese Academy of Science President’s International Fellowship Initiative (PIFI)(2020FSB0003)the Guangdong Retired Expert (granted by Guangdong Province)the Shenzhen Pengcheng ScientistNSFC-SNSF Funding (32161133022)Alpha Mol&SIAT Joint LaboratoryShenzhen Government Top-talent Working Funding and Guangdong Province Academician Work Funding。
文摘Drug discovery is a crucial part of human healthcare and has dramatically benefited human lifespan and life quality in recent centuries, however, it is usually time-and effort-consuming. Structural biology has been demonstrated as a powerful tool to accelerate drug development. Among different techniques, cryo-electron microscopy(cryo-EM) is emerging as the mainstream of structure determination of biomacromolecules in the past decade and has received increasing attention from the pharmaceutical industry. Although cryo-EM still has limitations in resolution, speed and throughput, a growing number of innovative drugs are being developed with the help of cryo-EM. Here, we aim to provide an overview of how cryo-EM techniques are applied to facilitate drug discovery. The development and typical workflow of cryo-EM technique will be briefly introduced, followed by its specific applications in structure-based drug design, fragment-based drug discovery, proteolysis targeting chimeras, antibody drug development and drug repurposing. Besides cryo-EM, drug discovery innovation usually involves other state-of-the-art techniques such as artificial intelligence(AI), which is increasingly active in diverse areas. The combination of cryo-EM and AI provides an opportunity to minimize limitations of cryo-EM such as automation, throughput and interpretation of mediumresolution maps, and tends to be the new direction of future development of cryo-EM. The rapid development of cryo-EM will make it as an indispensable part of modern drug discovery.
文摘Background Growth-differentiation factor-15(GDF-15)is a promising prognostic biomarker in patients with chronic heart failure (CHF).Comparatively little is known about the value of repeated measurement of GDF-15with CI-IF in Chinese Han population.This study sought to identify the clinical value of repeated measurement of GDF-15in Chinese Han patients with post-myocardial infarction CHF. Methods In total,232consecutive Chinese Hart patients with post-myocardial infarction CHF were enrolled prospectively from January 2014to June 2016.The plasma concentration of GDF-15was determined on admission and over 12months.Patients were followed up for all-cause death and a composite outcome of major adverse cardiac events (MACE)included all-cause death,myocardial infarction and first heart failure (HF)re-hospitalization.Association with other clinical variables and adverse outcomes of repeated measurement of GDF-15 was explored.Results The median baseline GDF-15level was 2025ng/L.Baseline GDF-15was moderately associated with baseline N-terminal pro-B type nalriuretic peptide (NT-proBNP)(coefficient 0.561,P <0.001).During a median follow-up of 20months,there were 53deaths and 100MACE.GDF-I5remained an independent predictor of all-cause death (adjusted hazard ratio 1.826per 1Ln U,95%CI: 1.037-8.360;P =0.037)and MACE (adjusted hazard ratio 2.243per I Ln U,95%CI:1.181-1.775;P <0.001)adjusted for established risk factors.Repeated measurement of GDF-15was performed in 173survivals over 12months.Increase of GDF-15over 12months was associ- ated with dilatation of left ventricle and acted as an independent predictor of subsequent all-canse death (adjusted HR =3.164,95%CI: 1.245~.041;P =0.015).In the joint model,GDF-15was also shown to be a risk factor for all-cause death (HR =2.749,95%CI: 1.667-3.831;P <0.001)and MACE (FIR =2.434,95%CI:1.425-3.443;P <0.001).Conclusions Repeated measurements of GDF-15 have promising prognostic value of the risk of all-cause death in Chinese Han patients with CI-IF post-myocardial infarction.GDF-15may influence the post-myocardial infarction CI-IF through the path physiological pathway of myocardial remodeling.
文摘AIM:To evaluate the role of probiotics in the standard triple Helicobacter pylori therapy.METHODS:In this meta-analysis,we investigated the efficacy of probiotics in a standard triple H.pylori therapy in adults.Searches were mainly conducted in MEDLINE/Pub Med,EMBASE,and the Cochrane Central Register of Controlled Trials.Fourteen studies met our criteria,and the quality of these studies was assessedusing the Jadad scale.We used STATA version 12.0to extract data and to calculate the odds ratios(ORs),which are presented with the corresponding 95%confidence intervals(CIs).The data are presented as forest plots.RESULTS:The pooled ORs for the eradication rates calculated by intention-to-treat analysis and perprotocol analysis in the probiotic group vs the control group were 1.67(95%CI:1.38-2.02)and 1.68(95%CI:1.35-2.08),respectively,using the fixed-effects model.The sensitivity of the Asian studies was greater than that of the Caucasian studies(Asian:OR=1.78,95%CI:1.40-2.26;Caucasian:OR=1.48,95%CI:1.06-2.05).The pooled OR for the incidence of total adverse effects was significantly lower in the probiotic group(OR=0.49,95%CI:0.26-0.94),using the random effects model,with significant heterogeneity(I2=85.7%).The incidence of diarrhea was significantly reduced in the probiotic group(OR=0.21,95%CI:0.06-0.74),whereas the incidence of taste disorders,metallic taste,vomiting,nausea,and epigastric pain did not differ significantly between the probiotic group and the control group.CONCLUSION:Supplementary probiotic preparations during standard triple H.pylori therapy may improve the eradication rate,particularly in Asian patients,and the incidence of total adverse effects.
基金financially supported by the National Key Research and Development Program of China(2016YFB0301200)
文摘This paper summarizes melting methods of titanium and titanium alloy, such as vacuum arc melting(VAR) and electron beam cold hearth melting(EBCHM), and the related inclusions formed when using these melting methods. Low-density inclusions are resulted from contamination of air, and high-density inclusions are caused by refractory elements. The formation process of inclusions was analysed. The removal mechanism of different kinds of inclusions was specified. Low-density inclusions are removed mainly by resolving. This is a comprehensive process containing reaction diffusion. The resolving rate of high-density inclusions is so low that these inclusions are mainly removed by sedimentation. The experiments and physical models of inclusions are detailed. In various melting methods, vacuum arc melting is prominent. However, this method cannot remove inclusions effectively, which usually results in repeat melting. Electron beam cold hearth melting has the best ability of removing inclusions. These results can provide instructions to researchers of titanium and titanium alloys.
文摘The infl uence of Si, Sn, Mo and Ni on the ductility and thermal conductivity of compacted graphite iron(CGI) was investigated. Metallographic observation and Differential Scanning Calorimetry(DSC) experiments were carried out to analyze the roles of various additions in the eutectoid reaction. The experimental results showed that the ductility of CGI is proportional to the ferrite fraction, so moderate Si content could dramatically improve the ductility by increasing the ferrite fraction. DSC measurements showed that Mo has moderate inhibition on eutectoid transformation during both the heating and cooling processes, while the sample without Sn obviously broadens the three-phase region. Vermicularity and ferrite are known to improve thermal conductivity, and the former plays a more important role. Besides, among the alloy elements investigated, Sn has the greatest negative effect on conductivity, followed by Ni and Mo having the smallest effects.
文摘As an excellent giant-magnetostrictive material, Tb-Dy-Fe alloys(based on Tb0.27-0.30Dy0.73-0.70Fe1.9-2Laves compound) can be applied in many engineering fields, such as sonar transducer systems, sensors, and micro-actuators. However, the cost of the rare earth elements Tb and Dy is too high to be widely applied for the materials. Nowadays, there are two different ways to substitute for these alloying elements. One is to partially replace Tb or Dy by cheaper rare earth elements, such as Pr, Nd, Sm and Ho; and the other is to use non-rare earth elements, such as Co, Al, Mn, Si, Ce, B, Be and C, to substitute Fe to form single MgCu_2-type Laves phase and a certain amount of Re-rich phase, which can reduce the brittleness and improve the corrosion resistance of the alloy. This paper systemically introduces the development, the fabrication methods and the corresponding preferred growth directions of Tb-Dy-Fe alloys. In addition, the effects of alloying elements and heat treatment on magnetostrictive and mechanical properties of Tb-Dy-Fe alloys are also reviewed, respectively. Finally, some possible applications of Tb-Dy-Fe alloys are presented.
基金supported by the National Natural Science Foundation of China(No.50974080)
文摘High-temperature mechanical properties of high-boron austenitic steels(HBASs) were studied at 850 °C using a dynamic thermal-mechanical simulation testing machine. In addition, the thermal fatigue properties of the alloys were investigated using the self-restraint Uddeholm thermal fatigue test, during which the alloy specimens were cycled between room temperature and 800°C. Stereomicroscopy and scanning electron microscopy were used to study the surface cracks and cross-sectional microstructure of the alloy specimens after the thermal fatigue tests. The effects of carbon content on the mechanical properties at room temperature and high-temperature as well as thermal fatigue properties of the HBASs were also studied. The experimental results show that increasing carbon content induces changes in the microstructure and mechanical properties of the HBASs. The boride phase within the HBAS matrix exhibits a round and smooth morphology, and they are distributed in a discrete manner. The hardness of the alloys increases from 239(0.19 wt.% C) to 302(0.29 wt.% C) and 312 HV(0.37 wt.% C); the tensile yield strength at 850 °C increases from 165.1 to 190.3 and 197.1 MPa; and the compressive yield strength increases from 166.1 to 167.9 and 184.4 MPa. The results of the thermal fatigue tests(performed for 300 cycles from room temperature to 800 °C) indicate that the degree of thermal fatigue of the HBAS with 0.29 wt.% C(rating of 2–3) is superior to those of the alloys with 0.19 wt.%(rating of 4–5) and 0.37 wt.%(rating of 3–4) carbon. The main cause of this difference is the ready precipitation of M23(C,B)6-type borocarbides in the alloys with high carbon content during thermal fatigue testing. The precipitation and aggregation of borocarbide particles at the grain boundaries result in the deterioration of the thermal fatigue properties of the alloys.
基金funded by the National Basic Research Program of China (973 Program, 2014CB845700)the National Natural Science Foundation of China (Grant Nos. 11390371)Funding for the project has been provided by the National Development and Reform Commission
文摘The Large sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST) general survey is a spectroscopic survey that will eventually cover approximately half of the celestial sphere and collect 10 million spectra of stars, galaxies and QSOs. Objects in both the pilot survey and the first year regular survey are included in the LAMOST DR1. The pilot survey started in October 2011 and ended in June 2012, and the data have been released to the public as the LAMOST Pilot Data Release in August 2012. The regular survey started in September 2012, and completed its first year of operation in June 2013. The LAMOST DR1 includes a total of 1202 plates containing 2 955 336 spectra, of which 1 790 879 spectra have observed signalto-noise ratio(SNR) ≥ 10. All data with SNR ≥ 2 are formally released as LAMOST DR1 under the LAMOST data policy. This data release contains a total of 2 204 696 spectra, of which 1 944 329 are stellar spectra, 12 082 are galaxy spectra and 5017 are quasars. The DR1 not only includes spectra, but also three stellar catalogs with measured parameters: late A,FGK-type stars with high quality spectra(1 061 918 entries), A-type stars(100 073 entries), and M-type stars(121 522 entries). This paper introduces the survey design, the observational and instrumental limitations, data reduction and analysis, and some caveats. A description of the FITS structure of spectral files and parameter catalogs is also provided.
基金Beijing Science and Technology Planning Project(Grant No.Z201100006720003)。
文摘Fe83Ga17 alloy is a kind of promising magnetostrictive alloys with high magnetostrictive properties and a low saturation magnetic field.As-cast Fe83Ga17 Dyx(x=0,0.05,0.1,0.2,0.4)polycrystalline alloys were prepared by arc melting.Effect of Dy doping on the microstructure,magnetostrictive and mechanical properties of as-cast Fe83Ga17 alloy was investigated.Results show that Dy-doped alloys exhibit a dual-phase structure containing the A2 matrix and Dy-rich precipitates(Fe56Ga34Dy10).Both magnetostriction and mechanical properties of Fe83Ga17 alloys are improved by Dy doping.A small amount of Dy addition(x=0.2)significantly causes Fe83Ga17 alloy to transform from typical brittle material(fracture strainε<1%)to plastic material(ε≈11%).Correspondingly,the fracture mode transforms from intergranular fracture to dimple fracture.At the same time,the ultimate tensile strength and the magnetostriction rise up to 209 MPa and 64 ppm,respectively.Dy-rich precipitates disperse along the grain boundries and inside the grains,which plays an important role in the grain refinement and solution strengthening,and therefore,contribute to the enhancement of mechanical properties of the alloy.The improvement of magnetostriction could be attributed to the large lattice distortion induced by Dy atoms entering into the A2 matrix.Doping Dy into Fe-Ga alloys provides an effective solution to the brittleness in their applications.
基金The Guoshoujing Telescope(GSJT)is a National Major Scientific Project built by the Chinese Academy of SciencesFunding for the project has been provided by the National Development and Reform Commission
文摘Planetary nebulae (PNe) are good tracers of the stellar populations, chemical composition and dynamics of their host galaxies. This paper reports the discovery of new PNe in the outskirts of the Andromeda Galaxy (M31) with the Guoshoujing Telescope (GSJT, formerly named the Large Sky Area Multi-Object Fiber Spectroscopic Telescope-LAMOST) during its early commissioning phase. In total, 36 candidates selected from SDSS photometry are confirmed in terms of their PN nature, including 17 new discoveries and another 19 previously known emission line objects. Their positions, spectra, radial velocities and m5007 magnitudes are presented. We discuss the potential for detecting more PNe in M 31 with GSJT's multi-object spectroscopy and the related applications in studies of the dynamics and chemistry of M 31 and its assemblage history.
基金supported by the National Key Basic Research Program of China(973Program,No.2014CB845700)the National Natural Science Foundation of China(Grant Nos.U1331120,U1431106,U1531118,U1531244 and 11473001)+1 种基金The Guo Shou Jing Telescope(the Large Sky Area MultiObject Fiber Spectroscopic Telescope,LAMOST)is aNational Major Scientific Project built by the Chinese Academy of Sciencesprovided by the National Development and Reform Commission.LAMOST is operated and managed by National Astronomical Observatories,Chinese Academy of Sciences
文摘The [α/Fe] ratios in stars are good tracers to probe the formation history of stellar populations and the chemical evolution of the Galaxy. The spectroscopic survey of LAMOST provides a good opportunity to determine [α/Fe] of millions of stars in the Galaxy. We present a method of measuring the [α/Fe]ratios from LAMOST spectra using the template-matching technique of the LSP3 pipeline. We use three test samples of stars selected from the ELODIE and MILES libraries, as well as the LEGUE survey to validate our method. Based on the test results, we conclude that our method is valid for measuring [α/Fe]from low-resolution spectra acquired by the LAMOST survey. Within the range of the stellar parameters Teff= [5000, 7500] K, log g = [1.0, 5.0] dex and [Fe/H]= [onsistent with values derived from high-resolution spectra,-1.5, +0.5] dex, our [α/Fe] measurements are c and the accuracy of our [α/Fe] measurements from LAMOST spectra is better than 0.1 dex with spectral signal-to-noise higher than 20.
文摘In order to improve the performance of plaster molds for investment casting,a diverse content of glass fiber and polypropylene(PP)fiber was incorporated into the slurry for the preparation of a fiber-reinforced mold.The green and fired bending strengths,thermal expansion properties,permeability,and thermal shock resistance of the mold were examined,and the scanning electron microscope(SEM)with energy dispersive spectrometer(EDS)was applied for the observation of fracture morphology.With appropriate content,the introduction of glass fiber was proved to increase the green bending strength and fired bending strength,restrain the thermal expansion and improve the thermal shock resistance of the mold,while the polypropylene fiber added was able to raise the green bending strength and the permeability,reduce the thermal expansion and heighten the thermal shock resistance as well,though the fired bending strength would be weakened slightly.Evenly distributed fibers were capable of enhancing the mechanical properties of the matrix,but agglomerations and bundles of fibers resulting from excessive addition had a negative impact.Meanwhile,it was also manifested that micropores left by ablative polypropylene fibers could improve the permeability and reduce the thermal expansion of the mold,and the fired bending strength would be decreased slightly by the deterioration of continuous structure.Three different ratios of hybrid fiber were employed in plaster molds,which can meet altered requirement of castings.The samples modified with hybrid fiber possessed lower thermal deformation,higher air permeability,and better resistance of thermal shock,while the mechanical strength was equal to the fiber free sample or slightly increased.
基金The Guoshoujing Telescope(GSJT)is a National Major Scientific Project built by the Chinese Academy of SciencesFunding for the project has been provided by the National Development and Reform Commission
文摘We present preliminary analyses of spectra of quasar candidates in two Guoshoujing Telescope (GSJT, formerly named the Large Sky Area Multi-Object Fiber Spectroscopic Telescope - LAMOST) test fields near M 31 where one is close to the optical center of the disk and the other is towards the northeastern outskirts of the halo, obtained during the early stage of the GSJT commissioning in the last season of 2009. Both fields contain background low-redshift quasar candidates selected from the SDSS photometry. In total, 14 new quasars with redshifts up to 2 and i magnitudes between 16.7 and 19.2, are discovered, including 7 within the 2.5° central region of M 31. We briefly discuss the potential applications of these newly discovered bright quasars.
基金supported by the Joint Funds of the National Natural Science Foundation of China (Grant No. U1531244)the National Key Basic Research Program of China (2014CB845700)+4 种基金support from the Young Researcher Grant of National Astronomical Observatories, Chinese Academy of Sciencessupported by Special Funding for Advanced Users, budgeted and administrated by the Center for Astronomical MegaScience, Chinese Academy of Sciences (CAMS)National Major Scientific Project built by the Chinese Academy of SciencesFunding for the project has been provided by the National Development and Reform CommissionNational Astronomical Observatories, Chinese Academy of Sciences
文摘We present extensive spectroscopic observations of supernova remnant (SNR) S 147 collected with the Large sky Area Multi-Object fiber Spectroscopic Telescope (LAMOST). The spectra were care- fully sky-subtracted taking into account the complex filamentary structure of S 147. We have utilized all available LAMOST spectra toward S 147, including sky and stellar spectra. By measuring the prominent optical emission lines including Ha, [NII] )λ 6584 and [S n] λλ6717, 6731, we present maps of radial velocity and line intensity ratio covering the whole nebula of S 147 with unprecedented detail. The maps spatially correlate well with the complex filamentary structure of S147. For the central 2° of S147, the radial velocity varies from - 100 to 100 krn s^-1 and has peaks between - 0 and 10 km s^-1. The intensity ratios of Hα/[S n)λλ6717,6731, [Sn] λ 6717/λ 6731 and Ha/IN Hα/λ 6584 peak at about 0.77, 1.35 and 1.48, respectively, with a scatter of 0.17, 0.19 and 0.37, respectively. The intensity ratios are consistent with the literature values. However, the range of variations of line intensity ratios estimated here, which are representative of the whole nebula, is larger than previously estimated.
基金the financial support by the National Natural Science Foundation of China(Grant No.51371104).
文摘Directionally solidified porous copper is considered as a potential candidate in the field of microchannel heat sinks.By the Bridgman-type directional solidification method,a porous copper ingot was fabricated.Evolution of the porosity,pore number density,average pore diameter and average interpore spacing at different ingot heights was investigated.The results show that with the increase of ingot height,the porosity firstly increases and then basically remains unchanged from the ignot height of 65 mm;the pore number density rapidly decreases at first,and the decreasing speed becomes slower when the ignot height higher than 85 mm;the average pore diameter increases and then remains unchanged from the ingot height of 85 mm;the average interpore spacing increases,and the increasing speed of average interpore spacing becomes slower with the increase of height to higher than 85 mm.In order to study the evolution of diameter and spatial distribution of pores,the distribution ranges of pore diameter,nearest-neighbor distance and radial cumulative pore number were analyzed.As the ingot height increases,the distribution ranges of pore diameter and nearest-neighbor distance firstly increase and then tend to be stable.There are no pore clusters and for long distance,the spatial distribution of pores is uniform at different ingot heights.Pore structure and 3D pore morphology of porous copper were observed with the help of light illumination and X-ray tomography.Pore nucleation,pore interruption,pore coalescence,diameter change of pores and lateral displacement of pores were found to exist in the pore structure.
基金supported by the National Key Basic Research Program of China (NKBRP) 2014CB845700supported by National Natural Science Foundation of China (Grant Nos.11473001 and 11233004)
文摘The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) published its first data release (DR1) in 2013, which is currently the largest dataset of stellar spectra in the world. We combine the PASTEL catalog and SIMBAD radial velocities as a testing standard to validate stellar parameters (effec- tive temperature Tefr, surface gravity log g, metallicity [Fe/H] and radial velocity Vr) derived from DR1. Through cross-identification of the DR1 catalogs and the PASTEL catalog, we obtain a preliminary sample of 422 stars. After removal of stellar param- eter measurements from problematic spectra and applying effective temperature con- straints to the sample, we compare the stellar parameters from DR1 with those from PASTEL and SIMBAD to demonstrate that the DR1 results are reliable in restricted ranges of Tefr. We derive standard deviations of 110 K, 0.19 dex and 0.11 dex for Tell, log 9 and [Fe/H] respectively when Teff〈 8000 K, and 4.91 km s-1 for Vr when Teff 〈 10 000 K. Systematic errors are negligible except for those of Vr. In addition, metallicities in DR1 are systematically higher than those in PASTEL, in the range of PASTEL [Fe/H] 〈 -1.5.
基金supported by the National Key Basic Research Program of China (2014CB845700)the National Natural Science Foundation of China (Grant No. 11473001)
文摘Using a sample of over 70 000 red clump(RC) stars with 5%–10% distance accuracy selected from the LAMOST Spectroscopic Survey of the Galactic Anti-center(LSS-GAC), we study the radial and vertical gradients of the Galactic disk(s) mainly in the anti-center direction, covering a significant volume of the disk in the range of projected Galactocentric radius 7 ≤ RGC ≤ 14 kpc and height from the Galactic midplane 0 ≤ |Z | ≤ 3 kpc. Our analysis shows that both the radial and vertical metallicity gradients are negative across much of the volume of the disk that is probed, and they exhibit significant spatial variations. Near the solar circle(7 ≤ RGC ≤ 11.5 kpc), the radial gradient has a moderately steep, negative slope of-0.08 dex kpc-1near the midplane(|Z | 〈 0.1 kpc), and the slope flattens with increasing |Z |. In the outer disk(11.5 〈 RGC ≤ 14 kpc), the radial gradients have an essentially constant, much less steep slope of-0.01 dex kpc-1at all heights above the plane, suggesting that the outer disk may have experienced an evolutionary path different from that of the inner disk. The vertical gradients are found to flatten largely with increasing RGC. However, the vertical gradient of the lower disk(0 ≤ |Z | ≤ 1 kpc)is found to flatten with RGC quicker than that of the upper disk(1 〈 |Z | ≤ 3 kpc).Our results should provide strong constraints on the theory of disk formation and evolution, as well as the underlying physical processes that shape the disk(e.g. gas flows,radial migration, and internal and external perturbations).