分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Radial colour gradients within galaxies arise from gradients of stellar age, metallicity and dust reddening. Large samples of colour gradients from wide-area imaging surveys can complement smaller integral-field spectroscopy datasets and can be used to constrain galaxy formation models. Here we measure colour gradients for low-redshift galaxies (z<0.1) using photometry from the DESI Legacy Imaging Survey DR9. Our sample comprises ~93,000 galaxies with spectroscopic redshifts and ~574,000 galaxies with photometric redshifts. We focus on gradients across a radial range 0.5 Re to Re, which corresponds to the inner disk of typical late type systems at low redshift. This region has been the focus of previous statistical studies of colour gradients and has recently been explored by spectroscopic surveys such as MaNGA. We find the colour gradients of most galaxies in our sample are negative (redder towards the centre), consistent with the literature. We investigate empirical relationships between colour gradient, average $g-r$ and $r-z$ colour, $M_r$, $M_\star$, and sSFR. Trends of gradient strength with $M_r$ ($M_\star$) show an inflection around $M_r\sim-21$ ($\log_{10} \, M_\star/\mathrm{M_\odot}\sim10.5$). Below this mass, colour gradients become steeper with increasing $M_\star$, whereas colour gradients in more massive galaxies become shallower. We find that positive gradients (bluer stars at smaller radii) are typical for galaxies of $M_{\star}\sim10^{8}\,\mathrm{M_\odot}$. We compare our results to age and metallicity gradients in two datasets derived from fits of different stellar population libraries to MaNGA spectra, but find no clear consensus explanation for the trends we observe. Both MaNGA datasets seem to imply a significant contribution from dust reddening, in particular, to explain the flatness of colour gradients along the red sequence.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Radial colour gradients within galaxies arise from gradients of stellar age, metallicity and dust reddening. Large samples of colour gradients from wide-area imaging surveys can complement smaller integral-field spectroscopy datasets and can be used to constrain galaxy formation models. Here we measure colour gradients for low-redshift galaxies (z<0.1) using photometry from the DESI Legacy Imaging Survey DR9. Our sample comprises ~93,000 galaxies with spectroscopic redshifts and ~574,000 galaxies with photometric redshifts. We focus on gradients across a radial range 0.5 Re to Re, which corresponds to the inner disk of typical late type systems at low redshift. This region has been the focus of previous statistical studies of colour gradients and has recently been explored by spectroscopic surveys such as MaNGA. We find the colour gradients of most galaxies in our sample are negative (redder towards the centre), consistent with the literature. We investigate empirical relationships between colour gradient, average $g-r$ and $r-z$ colour, $M_r$, $M_\star$, and sSFR. Trends of gradient strength with $M_r$ ($M_\star$) show an inflection around $M_r\sim-21$ ($\log_{10} \, M_\star/\mathrm{M_\odot}\sim10.5$). Below this mass, colour gradients become steeper with increasing $M_\star$, whereas colour gradients in more massive galaxies become shallower. We find that positive gradients (bluer stars at smaller radii) are typical for galaxies of $M_{\star}\sim10^{8}\,\mathrm{M_\odot}$. We compare our results to age and metallicity gradients in two datasets derived from fits of different stellar population libraries to MaNGA spectra, but find no clear consensus explanation for the trends we observe. Both MaNGA datasets seem to imply a significant contribution from dust reddening, in particular, to explain the flatness of colour gradients along the red sequence.
分类： 核科学技术 >> 核材料与工艺技术 提交时间： 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要： Sweet sorghum has the potential of becoming a useful energy crop. An early-maturity mutant of sweet sorghum, KFJT-1, was obtained by carbon ions irradiation of KFJT-CK, a wild plant. In this paper, we evaluate the mutant from the length and fresh weight of radicle and leaves after seed germination, the growth rate at the elongation stage, and the internodal parameters under field trail condition. The results showed that the seedling growth of KFJT-1 was inhibited by carbon ions irradiation, and the leaf length, the fresh weight of radicle and leaves from KFJT-1 decreased by 15.32%, 76.27%, and 27.08% than those of KFJT-CK, respectively. However, the growth rate of KFJT-1 on July 12, July 27 and August 1 increased by 16.19%, 59.28% and 26.87%, respectively, compared with the KFJT-CK. The stalk diameter, total biomass yield and sugar content of KFJT-1 was higher than those of KFJT-CK, despite that the plant height of KFJT-1 was significantly less than KFJT-CK (P<0.05). In addition, KFJT-1 differed from KFJT-CK in the internodal length, weight and sugar content. In conclusion, the early-maturity mutant of KFJT-1 will be a promising variety for sweet sorghum industrialization in Gansu province, China.
分类： 地球科学 >> 地理学 提交时间： 2023-06-13 合作期刊: 《干旱区科学》
摘要：The mineral dust emitted from Central Asia has a significant influence on the global climate system. However, the history and mechanisms of aeolian activity in Central Asia remain unclear, due to the lack of well-dated records of aeolian activity and the intense wind erosion in some of the dust source areas (e.g., deserts). Here, we present the records of aeolian activity from a sedimentary sequence in the southern Gurbantunggut Desert of China using grain size analysis and optically stimulated luminescence (OSL) dating, based on field sampling in 2019. Specifically, we used eight OSL dates to construct chronological frameworks and applied the end-member (EM) analysis for the grain size data to extract the information of aeolian activity in the southern Gurbantunggut Desert during the last 900 a. The results show that the grain size dataset can be subdivided into three EMs (EM1, EM2, and EM3). The primary modal sizes of these EMs (EM1, EM2, and EM3) are 126.00, 178.00, and 283.00 μm, respectively. EM1 represents a mixture of the suspension components and saltation dust, while EM2 and EM3 show saltation dust transported over a shorter distance via strengthened near-surface winds, which can be used to trace aeolian activity. Combined with the OSL chronology, our results demonstrate that during the last 900 a, more intensive and frequent aeolian activity occurred during 450–100 a BP (Before Present) (i.e., the Little Ice Age (LIA)), which was reflected by a higher proportion of the coarse-grained components (EM2+EM3). Aeolian activity decreased during 900–450 a BP (i.e., the Medieval Warm Period (MWP)) and 100 a BP–present (i.e., the Current Warm Period (CWP)). Intensified aeolian activity was associated with the strengthening of the Siberian High and cooling events at high northern latitudes. We propose that the Siberian High, under the influence of temperature changes at high northern latitudes, controlled the frequency and intensity of aeolian activity in Central Asia. Cooling at high northern latitudes would have significantly enhanced the Siberian High, causing its position to shift southward. Subsequently, the incursion of cold air masses from high northern latitudes resulted in stronger wind regimes and increased dust emissions from the southern Gurbantunggut Desert. It is possible that aeolian activity may be weakened in Central Asia under future global warming scenarios, but the impact of human activities on this region must also be considered.
分类： 物理学 >> 核物理学 提交时间： 2025-03-11
摘要： This paper explores the impact of back-gate bias ( Vsoi ) and supply voltage ( VDD ) on the single-eventupset (SEU) cross section of 0.18 µm configurable silicon-on-insulator (CSOI) static random-access memory(SRAM) under high linear energy transfer (LET) heavy-ion experimentation. The experimental findings demon#2;strate that applying a negative back-gate bias to NMOS and a positive back-gate bias to PMOS enhances theSEU resistance of SRAM. Specifically, as the back-gate bias for N-type transistors ( Vnsoi ) decreases from0 to −10 V, the SEU cross section decreases by 93.23%, whereas an increase in the back-gate bias for P-typetransistors ( Vpsoi ) from 0 V to 10 V correlates with an 83.7% reduction in SEU cross section. Furthermore, asignificant increase in the SEU cross section was observed with increasing supply voltage, as evidenced by a159% surge at VDD = 1.98 V compared with the nominal voltage of 1.8 V. To explore the physical mechanismsunderlying these experimental data, we analyzed the dependence of the critical charge of the circuit and thecollected charge on the bias voltage by simulating SEUs using technology computer aided design (TCAD).
分类： 物理学 >> 核物理学 提交时间： 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要： The reliability of radiotherapy was evaluated and effective approaches were obtained in order to improve radiotherapy quality by using the Probabilistic Safety Assessment (PSA) method. This study investigated the feasibility of the PSA method being applied to radiotherapy through Image-guided Radiotherapy (IGRT) and chest tumor irradiation. A fault tree has been constructed after analyzing causal relationship of the events. After calculating RiskA, a total inaccuracy radiotherapy probability and the importance of all base events were obtained. The probability of inaccurate radiotherapy was 2.87%. Under the condition that the target delineation was perfectly right, the accuracy of radiotherapy significantly improved. With the calculation without Cone-beam Computed Tomography (CBCT) being corrected before irradiation, the accuracy significantly decreased. The most important events were connected with the human factor. Improving human technical level could enhance radiotherapy quality control efficiently.
分类： 天文学 >> 天文学 提交时间： 2025-04-28 合作期刊: 《Research in Astronomy and Astrophysics》
摘要： Indirect X-ray modulation imaging has been adopted in a number of solar missions and provided reconstructed X-ray images of solar flares that are of great scientific importance. However, the assessment of the image quality of the reconstruction is still difficult, which is particularly useful for scheme design of X-ray imaging systems, testing and improvement of imaging algorithms, and scientific research of X-ray sources. Currently, there is no specified method to quantitatively evaluate the quality of X-ray image reconstruction and the point-spread function (PSF) of an X-ray imager. In this paper, we propose percentage proximity degree (PPD) by considering the imaging characteristics of X-ray image reconstruction and in particular, sidelobes and their effects on imaging quality. After testing a variety of imaging quality assessments in six aspects, we utilized the technique for order preference by similarity to ideal solution to the indices that meet the requirements. Then we develop the final quality index for X-ray image reconstruction, QuIX, which consists of the selected indices and the new PPD. QuIX performs well in a series of tests, including assessment of instrument PSF and simulation tests under different grid configurations, as well as imaging tests with RHESSI data. It is also a useful tool for testing of imaging algorithms, and determination of imaging parameters for both RHESSI and ASO-S/Hard X-ray Imager, such as field of view, beam width factor, and detector selection.
分类： 核科学技术 >> 核材料与工艺技术 提交时间： 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要： In this paper, the growth curves of yeast cells exposed to X-rays were detected, and then fitted by Gompertz equation. The yeast cells treated with 50125 Gy showed an increased exponential growth rate, and lower total biomass at plateau. At doses 150 Gy, cells showed a decreased exponential growth rate and higher total biomass at plateau. DNA lesions were detected by comet assay. Meanwhile, intracellular accumulation of reactive oxygen species (ROS), reduction of mitochondrial membrane potential (m) and cell membrane integrity were evaluated. We conclude that X-ray irradiation results in DNA lesions, ROS accumulation and m decline in a dose-dependent manner, and that these changes may be one of causes of X-rays-induced apoptosis in yeast. Furthermore, yeast cell membrane integrity appeared compromised following irradiation, suggesting that membrane damage may also have a role in the biological effects of radiation.
分类： 核科学技术 >> 核材料与工艺技术 提交时间： 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要： To study cytotoxic effect of heavy ion irradiation in the plateau region, and investigate whether autophagy induced by heavy ion irradiation is cytoprotective, HeLa cells were irradiated with 350 MeV/u carbon ions beams, and the clonogenic survival was analyzed. The results showed that cell survival decreased with increasing doses. It was also found that G2/M-phase cells increased, and the autophagy-related activity was significantly higher than the control. When autophagy was blocked by 3-methyladenine in carbon-ion irradiated cells, G2/M phase arrest and the percentage of apoptosis cells were further elevated, and cell survival decreased significantly, indicating the induction of cytoprotective autophagy by carbon-ion irradiation. Our results demonstrated that autophagy induced by carbon ion irradiation provided a self-protective mechanism in HeLa cells, short-time inhibition of autophagy before carbon-ion irradiation could enhance radiation cytotoxicity in HeLa cells.
分类： 核科学技术 >> 核材料与工艺技术 提交时间： 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要： In this study, strains of Aspergillus niger 4# for hyper citric acid were irradiated to different doses by 80 MeV/u 12C6+ ion beams. Seven mutant strains showed marked citric acid over-production records and faster productivity than initial Aspergillus niger 4# by shaking flash fermentation. The maximum product yield was 132.8 -g L-1( the H4002 strain) being a 8.8% increase to the initial strain. The scale-up experiment was carried out in a 100 L bioreactor. The mutant H4002 can accumulate 187 -g L-1 product yield of citric acid from starch liquefying supernatant. The productivity of citric acid was 2.75 g L-1 h-1. So, the mutant H4002 possesses rapid sugar katabolism for producing citric acid. Meanwhile, the pellet morphology kept compact and round during the whole submerged fermentation, which was suited to produce citric acid. The results indicate that mutant H4002 has potential ability to produce citric acid rapidly.
分类： 核科学技术 >> 粒子加速器 提交时间： 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要： Induced radioactivity is one of the essential problems in the radiation protection field of proton accelerators. Research on the induced radioactivity of low-energy proton accelerators is highly limited. Given such context, this study investigates the cross section of 63Cu (p, n) 63Zn and 65Cu (p, n) 65Zn in Cu targets at 11 MeV proton accelerators through an activation experiment. The uncertainties of the results are analyzed in detail. Results show that the cross section of the reaction of 65Cu (p, n) 65Zn in the experiment is only 1.36% lower than that of the FLUKA simulation, whereas the reaction of 63Cu (p, n) 63Zn in the experiment is 25.4% higher than that of the FLUKA simulation. Given that the benchmark for the FLUKA code of low-energy proton accelerators is very limited, this study provides a reference in this field.
分类： 天文学 >> 天文学 提交时间： 2025-04-28 合作期刊: 《Research in Astronomy and Astrophysics》
摘要： To address the issues of low accuracy and high computational complexity in traditional channelization techniques for ultra-wideband signals, this paper proposes a novel rationally oversampled channelization method to enhance the accuracy and efficiency of signal processing. The proposed method is evaluated by implementing and comparing critically sampled and integer oversampled channelization algorithms. A detailed analysis of the impact of different oversampling factors and filter orders on performance is provided. The validity of the proposed algorithm is verified using baseband data from pulsar J0437−4715 observed by the Parkes telescope, demonstrating its effectiveness and correctness.
分类： 生物学 >> 生物物理学 提交时间： 2016-05-12
Xing, Mengtan
Huo, Wei
Ning, Shaokai
Yan, Zhenxin
Li, Wen
Wang, Qingsong
Hou, Mei
Dong, Chunxia
Guo, Rong
Gao, Ge
Ji, Jianguo
Xu, Dongyi
Yang, Mingrui
Feng, Feng
Liang, Huanhuan
Yang, Mingrui
Wei, Leizhen
Lan, Li
Jiang, Wenxia
Zha, Shan
摘要： Non-homologous end joining (NHEJ) is a major pathway to repair DNA double-strand breaks (DSBs), which can display different types of broken ends. However, it is unclear how NHEJ factors organize to repair diverse types of DNA breaks. Here, through systematic analysis of the human NHEJ factor interactome, we identify PAXX as a direct interactor of Ku. The crystal structure of PAXX is similar to those of XRCC4 and XLF. Importantly, PAXX-deficient cells are sensitive to DSB-causing agents. Moreover, epistasis analysis demonstrates that PAXX functions together with XLF in response to ionizing radiation-induced complex DSBs, whereas they function redundantly in response to Topo2 inhibitor-induced simple DSBs. Consistently, PAXX and XLF coordinately promote the ligation of complex but not simple DNA ends in vitro. Altogether, our data identify PAXX as a new NHEJ factor and provide insight regarding the organization of NHEJ factors responding to diverse types of DSB ends.
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