An ultrasensitive resonance rayleigh scattering(RRS) method for the determination of trace octreotide was developed. The determination of octreotide in an octreotidemethyl red system via RRS was studied comprehensively. In a pH=3.78 B-R buffer solution, the RRS intensity is enhanced obviously in the range of 280~370 nm as octreotide associates with methyl red. The strongest ΔIRRS is at 310 nm. The RRS intensitiy of octreotide is proportional to the concentration of octreotide over the range of 0~0.54 mg/L, the detection limit for the octreotide(3σ) is 3.6 μg/L under optimum conditions. The method was applied to the determination of octreotide in synthetic samples with the recovery of 98.3%~100.7%. Measurements of the commercial injection samples also gave satisfactory results which were in good agreement with those obtained using high performance liquid chromatography(HPLC) method.
The infrared excess from OB stars are commonly considered as contributions from ionized stellar wind or circumstellar dust. With the newly published LAMOST-OB catalog and GOSSS data, this work steps further on understanding the infrared excess of OB stars. Based on a forward modeling approach comparing the spectral slope of observational Spectral Energy Distributions (SED) and photospheric models, 1147 stars are found to have infrared excess from 7818 stars with good-quality photometric data. After removing the objects in the sightline of dark clouds, 532 ($\sim7\%$) B-type stars and 118 ($\sim23\%$) O-type stars are identified to be true OB stars with circumstellar infrared excess emission. The ionized stellar wind model and the circumstellar dust model are adopted to explain the infrared excess, and Bayes Factors are computed to quantitatively compare the two. It is shown that the infrared excess can be accounted for by the stellar wind for about 65\% cases in which 33\% by free-free emission and 32\% by synchrotron radiation. Other 30\% sources could have and 4\% should have a dust component or other mechanisms to explain the sharply increase flux at $λ> 10μ$m. The parameters of dust model indicate a large-scale circumstellar halo structure which implies the origin of the dust from the birthplace of the OB stars. A statistical study suggests that the proportion with infrared excess in OB stars increases with stellar effective temperature and luminosity, and that there is no systematic change of the mechanism for infrared emission with stellar parameters.
We report the discovery of a unique quasar-dusty star-forming galaxy (DSFG) system at $z = 5.63$, consisting of the bright quasar J1133+1603 ($M_{\rm UV} = -27.42$) and its compact, dust-obscured companion, J1133c. ALMA observations reveal a prominent [C II] bridge connecting the quasar and DSFG, indicating ongoing interaction at a projected separation of 1.8 arcsec ($\sim$10 proper kpc). J1133c exhibits unusually bright and broad [C II] emission ($L_{\rm [CII]} > 10^{43}$ erg s$^{-1}$, FWHM $> 500$ km s$^{-1}$), with a [C II] luminosity five times that of the quasar, suggesting intense star formation or potential AGN activity. The inferred star formation rate from [C II] is approximately $10^3$ M$_\odot$ yr$^{-1}$. The remarkable properties of this pair strongly suggest that galaxy interactions may simultaneously trigger both starburst and quasar activity, driving rapid evolution in the early universe.
Abstract The Chinese Space Station Telescope (CSST) spectroscopic survey aims to deliver high-quality low-resolution ( R > 200) slitless spectra for hundreds of millions of targets down to a limiting magnitude of about 21 mag, distributed within a large survey area (17 500 deg 2 ) and covering a wide wavelength range (255–1000 nm by three bands GU, GV, and GI). As slitless spectroscopy precludes the usage of wavelength calibration lamps, wavelength calibration is one of the most challenging issues in the reduction of slitless spectra, yet it plays a key role in measuring precise radial velocities of stars and redshifts of galaxies. In this work, we propose a star-based method that can monitor and correct for possible errors in the CSST wavelength calibration using normal scientific observations, taking advantage of the facts that (i) there are about ten million stars with reliable radial velocities now available thanks to spectroscopic surveys like LAMOST, (ii) the large field of view of CSST enables efficient observations of such stars in a short period of time, and (iii) radial velocities of such stars can be reliably measured using only a narrow segment of CSST spectra. We demonstrate that it is possible to achieve a wavelength calibration precision of a few km s −1 for the GU band, and about 10 to 20 km s −1 for the GV and GI bands, with only a few hundred velocity standard stars. Implementations of the method to other surveys are also discussed.
Food security is one of the main challenges facing humanity, and increasing crop yields is critical to meet the growing global food demand. Grain production in China has remarkably improved since its founding in 1949, but the growth remains uneven across regions. The goal of this research was to assess the determinants of the yields of three major food crops (maize, rice, and wheat) in China and the mechanism of their responses to increased crop yields. Boosted regression tree models were created to capture the linked complex predictor-response relationships between crop yields and individual explanatory variables using prefecture-level agricultural statistics in China during the period from 1952 to 2017. The results showed that technological inputs (e.g., fertilizers and electricity consumption) played a key role in the increase of crop yields, which explained 47%, 39%, and 62% of the variances in the yields of maize, rice, and wheat during the period 1952–2017, respectively. However, the contribution of technology became weaker over time, while the contribution of agro-environmental conditions and structural characteristics of administrative regions became stronger. Partial dependence plots indicated that encouraging higher technological inputs, accelerating large-scale grain production, shortening the urban-rural income gap, and improving the education of farmers were conductive to increasing crop yields. Overall, our results suggest that grain production policies aimed at increasing crop yields should better reflect the spatial heterogeneity of yield gaps; low-yield-gap regions should improve the utilization efficiency of water and fertilizer and formulate measures to inhibit non-grain production on cultivated land, while high-yield-gap regions should focus on improving technological inputs and promoting agricultural restructuring. This study provides deep insights into the processes of how individual explanatory variables affect crop yields, which is essential to develop differentiated grain production policies and provide valuable references for shortening yield gaps in high-yield-gap regions.
This is the first time that the microwave performance of a 0.1-/spl mu/m gate in a silicon nitride window opening, with a field-modulating plate on an AlGaN/AlN/GaN heterojunction structure, is reported. The material structure was grown by organometallic vapor phase epitaxy on SiC substrates with an averaged channel sheet resistance of 313.5 ohms/square. Approximately 80-nm-thick plasma-enhanced chemical vapor deposition silicon nitride is used as the dielectric between gate metal extension and semiconductor surface. Transistors of a total gate width of 250 /spl mu/m and a 0.1 /spl mu/m gate footprint, with a 0.36 /spl mu/m long overhang on top of the silicon nitride, can be operated at a drain bias of 40-V high. Output power density of 9.5 W/mm, with 36% power-added efficiency in class AB regime, was demonstrated at 10 GHz in a continuous wave power measurement.
Abstract We report the discovery of a unique quasar-dusty star-forming galaxy (DSFG) system at z = 5.63, consisting of the bright quasar J1133+1603 ( M UV = − 27.42) and its compact, dust-obscured companion, J1133c. ALMA observations reveal a prominent [C II ] bridge connecting the quasar and DSFG, indicating ongoing interaction at a projected separation of 1 .″ 8 (∼10 proper kpc). J1133c exhibits unusually bright and broad [C II ] emission ( L [C II ] > 10 43 erg s −1 , FWHM > 500 km s −1 ), with a [C II ] luminosity five times that of the quasar, suggesting intense star formation or potential active galactic nucleus activity. The inferred star formation rate from [C II ] is approximately 10 3 M ⊙ yr −1 . The remarkable properties of this pair strongly suggest that galaxy interactions may simultaneously trigger both starburst and quasar activity, driving rapid evolution in the early universe.
Precise correction of dust reddening is fundamental to obtain the intrinsic parameters of celestial objects. The Schlegel et al. (SFD) and the Planck 2D extinction maps are widely used for the reddening correction. In this work, using accurate reddening determinations of about two million stars from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) data release 5 (DR5) and Gaia DR2, we check and calibrate the SFD and Planck maps in the middle and high Galactic latitudes. The maps show similar precision in reddening correction. We find small yet significant spatially dependent biases for the four maps, which are similar between the SFD and Planck2014-R maps, and between the Planck2014-Tau and Planck2019-Tau maps. The biases show a clear dependence on the dust temperature and extinction for the SFD and Planck2014-R maps. While those of the Planck2014-Tau and Planck2019-Tau maps have a weak dependence on the dust temperature, they both strongly depend on the dust spectral index. Finally, we present corrections of the SFD and Planck extinction maps within the LAMOST footprint, along with empirical relations for corrections outside the LAMOST footprint. Our results provide important clues for the further improvement of the Galactic all-sky extinction maps and lay an significant foundation for the accurate extinction correction in the era of precision astronomy.
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