期刊文献+
共找到150,995篇文章
< 1 2 250 >
每页显示 20 50 100
Distribution and geochemical significance of alkylbenzenes for crude oil with different depositional environments and thermal maturities
1
作者 Bing-Kun Meng Dao-Fu Song +1 位作者 Yuan Chen Sheng-Bao Shi 《Petroleum Science》 SCIE EI CAS CSCD 2024年第2期777-790,共14页
A total of 45 alkylbenzenes were detected and identified in crude oils with different depositional environments and thermal maturities from the Tarim Basin,Beibuwan Basin,and Songliao Basin using comprehensive two-dim... A total of 45 alkylbenzenes were detected and identified in crude oils with different depositional environments and thermal maturities from the Tarim Basin,Beibuwan Basin,and Songliao Basin using comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry(GC×GCTOFMS).By analyzing the distribution characteristics of C0-C5alkylbenzenes,it is found that the content of some alkylbenzenes varies greatly in crude oils.Based on the distribution characteristics of 1,2,4,5-tetramethylbenzene(Te MB)and 1,2,3,4-Te MB,the ratio of 1,2,4,5-Te MB to 1,2,3,4-Te MB is proposed to indicate the organic matter origin and depositional environment of ancient sediments.Oil samples originated mainly from lower hydrobiont,algae,bacteria and source rocks deposited under reducing/anoxic conditions have low 1,2,4,5-/1,2,3,4-Te MB values(less than 0.6),while oil samples originated mainly from terrestrial higher plants and source rocks deposited under oxic/sub-oxic conditions have higher 1,2,4,5-/1,2,3,4-Te MB values(greater than 1.0).The significant difference of 1,2,4,5-/1,2,3,4-Te MB values is controlled by 1,2,4,5-Te MB content.1,2,4,5-Te MB content in oils derived from source rocks deposited in oxidized sedimentary environment(greater than 1.0 mg/g whole oil)is higher than that in oils from source rocks deposited in reduced sedimentary environment(less than 1.0 mg/g whole oil).1,2,4,5-/1,2,3,4-Te MB ratio might not or slightly be affected by evaporative fractionation,biodegradation and thermal maturity.1,2,4,5-/1,2,3,4-Te MB ratio and 1,2,4,5-Te MB content can be used as supplementary parameter for the identification of sedimentary environment and organic matter input.It should be noted that compared to the identification of organic matter sources,the 1,2,4,5-/1,2,3,4-Te MB parameter is more effective in identifying sedimentary environments. 展开更多
关键词 1 2 4 5-Tetramethylbenzene GC×GC-TofMS Organic matter origin Depositional environment
下载PDF
Clinical Application of Sex Hormone in Different Physiological Periods in the Diagnosis of Infertility Patients
2
作者 Jianhong Nong Daxian Tan +4 位作者 Arshad Mehmood Tingchao Wang Xin Liu Li Deng Bowen Wei 《Natural Science》 2024年第6期102-110,共9页
Background: Infertility is characterized by the inability to conceive after a year of regular unprotected intercourse. Aims: This study aimed to investigate the diagnostic value of sex hormone levels during different ... Background: Infertility is characterized by the inability to conceive after a year of regular unprotected intercourse. Aims: This study aimed to investigate the diagnostic value of sex hormone levels during different physiological periods in the diagnosis of infertility patients. Methods: From December 2019 to May 2021, a total of 93 infertility patients were admitted and selected as the observation group. Among them, 31 cases were in the follicular stage, 31 cases in the ovulation stage, and 31 cases in the luteal stage. Ninety-three healthy women for fertility evaluation due to male infertility were selected as the control group. The control group included 31 women in the follicular phase, 31 women in the ovulatory phase, and 31 women in the luteal phase. The levels of sex hormones (prolactin (PRL), luteinizing hormone (LH), follicle-stimulating hormone (FSH), estradiol (E2), testosterone (T), and progesterone (P)) during different physiological phases were compared between the observation and control groups. Results: The follicular phase showed no significant difference in LH levels between the observation group and the control group. The observation group showed higher levels of PRL and P compared to the control group, while the levels of FSH, E2, and T were lower in the observation group compared to the control group. The ovulation phase showed no significant difference in PRL levels between the two groups. The observation group showed lower levels of LH, FSH, E2, T, and P compared to the control group. The luteal phase showed no statistical difference in E2 levels between the two groups. The observation group showed higher levels of PRL, LH, and FSH compared to the control group, while the levels of T and P were lower in the observation group compared to the control group. Conclusion: Infertile women show variations in hormone levels compared to the normal levels during the follicular phase, ovulatory phase, and luteal phase. 展开更多
关键词 different Periods Sex Hormone Level Detection INFERTILITY Auxiliary Diagnosis
下载PDF
Solving the Olbers’s Paradox, Explaining the “Red-Shift”, and Challenging the Relativities by “Sun Matters Theory” and “Sun Model of Universe”, an Evolution of the Einstein’s Static Universe Model
3
作者 Wanpeng Sun 《Natural Science》 2024年第2期7-18,共12页
Olbers’s paradox, known as the dark night paradox, is an argument in astrophysics that the darkness of the night sky conflicts with the assumption of an infinite and eternal static universe. Big-Bang theory was used ... Olbers’s paradox, known as the dark night paradox, is an argument in astrophysics that the darkness of the night sky conflicts with the assumption of an infinite and eternal static universe. Big-Bang theory was used to partially explain this paradox, while introducing new problems. Hereby, we propose a better theory, named Sun Matters Theory, to explain this paradox. Moreover, this unique theory supports and extended the Einstein’s static universe model proposed by Albert Einstein in 1917. Further, we proposed our new universe model, “Sun Model of Universe”. Based on the new model and novel theory, we generated innovative field equation by upgrading Einstein’s Field Equation through adding back the cosmological constant, introducing a new variable and modifying the gravitationally-related concepts. According to the Sun Model of Universe, the dark matter and dark energy comprise the so-called “Sun Matters”. The observed phenomenon like the red shift is explained as due to the interaction of ordinary light with Sun Matters leading to its energy and frequency decrease. In Sun Model, our big universe consists of many universes with ordinary matter at the core mixed and surrounded with the Sun Matters. In those universes, the laws of physics may be completely or partially different from that of our ordinary universe with parallel civilizations. The darkness of night can be easily explained as resulting from the interaction of light with the Sun Matters leading to the sharp decrease in the light intensity. Sun Matters also scatter the light from a star, which makes it shining as observed by Hubble. Further, there is a kind of Sun Matters named “Sun Waters”, surrounding every starts. When lights pass by the sun, the Sun Waters deflect the lights to bend the light path. According to the Sun Model, it is the light bent not the space bent that was proposed in the theory of relativities. 展开更多
关键词 Olbers’s Paradox Sun matters theory Sun Model of Universe Einstein’s Universe Dark Mass
下载PDF
Effects of different processing methods on the quality of Polygonatum cyrtonema Hua
4
作者 Xin-Ning Zhang Shuang-Hui Shi +13 位作者 Jun-Li Zhang Fan-Miao Kong Hai-Ting Zhu Si-Yuan Ma Yu-Feng Hu Ming-Rui Jiang Hui-Nan Wang Meng-Lin Wang Xiao-Tong Wei Jing-Qiu Zhang Nan Sun Meng-Yu Chen Qian-Qian Liu Ying-Zi Wang 《TMR Modern Herbal Medicine》 CAS 2024年第2期28-34,共7页
Background:In this study,we explored the effects of different processing methods on the quality of Polygonatum cyrtonema Hua(PC),and the role of Huangjiu in the processing procedure.Methods:The sensory characteristics... Background:In this study,we explored the effects of different processing methods on the quality of Polygonatum cyrtonema Hua(PC),and the role of Huangjiu in the processing procedure.Methods:The sensory characteristics of the crude product,steamed product,and wine-processed product of PC were described.The colorimeter was used to analyze the chromatic values of three different processed products on PC.At the same time,the contents of the water extract and alcohol extract were measured separately.The content of three different processing Polygonatum Polysaccharide(PCP)was determined using 0.2%anthrone-sulfuric acid.The correlation difference between the chromatic values and chemical composition of different PC products was analyzed using various analytical methods.Results:The surface colors gradually deepened,the sweetness increased,the viscosity strengthened,and the tongue-numbing sensation disappeared after PC processing.The contents of extract and L^(*) gradually decreased from the crude to the steamed to the wine-processed product,consistent with the pattern of surface color alteration.While,E^(*)ab gradually increased.The content of PCP was crude product>wine-processed product>steamed product.The results of multivariate statistical analysis showed that the samples processed for crude,steamed,and wine-processed product were clustered into three classes.The correlation analysis showed that L^(*)and E^(*)ab were highly significant positively correlated with the content of PCP,and a*was significantly negatively correlated with the content of PCP.Conclusion:The results showed that the wine-processed product had the best quality.The internal quality of the PC was correlated with its characteristics and chromatic value.In this study,we investigated the internal and external quality of three different products of PC in order to provide a reference for further research on the impact of different processing methods on PC quality,the standardization of PC processing,and the role of Huangjiu in the processing of PC. 展开更多
关键词 Polygonatum cyrtonema Hua different products chemical composition chromatic value CHARACTERISTICS
下载PDF
Exploring the mechanism of electroacupuncture at different acupoints on acute colitis rats based on JAK2/STAT3/SOCS1 signaling pathway
5
作者 ZHANG Chun-qing TANG Kun-peng +2 位作者 YAN Li-ping WEN Tan WANG Hai-jun 《Journal of Hainan Medical University》 CAS 2024年第3期1-7,共7页
Objective:To investigate the mechanism of JAK2/STAT3/SOCS1 signaling pathway in electroacupuncture of different acupoints on acute colitis rats.Methods:36 SPF SD rats were randomly divided into 6 groups,with 6 rats in... Objective:To investigate the mechanism of JAK2/STAT3/SOCS1 signaling pathway in electroacupuncture of different acupoints on acute colitis rats.Methods:36 SPF SD rats were randomly divided into 6 groups,with 6 rats in each group.The rat model of acute colitis was prepared by enema with glacial acetic acid solution.After the model was established,electroacupuncture was given to each acupoint group,with density wave,frequency 2Hz-50 Hz,intensity 2 mA,muscle tremor as the degree 20 min/time,1 time/day,for 3 consecutive days.Observe the general condition of rats;the pathological changes of colonic mucosa in rats were observed by HE method.The contents of serum interleukin-4(IL-4)and interleukin-8(IL-8)were detected by ELISA.Western blot and RT-PCR were used to detect the expression of JAK2,STAT3,SOCS1 protein and mRNA in rat colon tissue.Results:In contrast to the normal group,the overall condition of the model group was worse,the colonic mucosa was severely damaged,even necrotic,and the ulcer surface was obvious.The content of IL-4 in serum was obviously reduced,and the content of IL-8 was obviously go up(P<0.01).The protein content of JAK2,STAT3 and the expression of JAK2,STAT3 mRNA in colon tissue of rats were obviously go up,while the protein content of SOCS1 and the expression of SOCS1 mRNA were obviously reduced(P<0.01).In contrast to the model group,the general condition of rats in each acupoint group was significantly improved,the damage and necrosis of colonic mucosa and ulcer surface were obviously alleviated,the content of IL-4 in serum was obviously go up,and the content of IL-8 was significantly decreased(P<0.01).The protein content of JAK2,STAT3 and the expression of JAK2,STAT3 mRNA in colon tissue of rats were obviously reduced,while the protein content of SOCS1 and the expression of SOCS1 mRNA were obviously go up(P<0.05,P<0.01).Comparison of different acupoint groups,the colonic mucosal injury in the Zusanli group was significantly reduced,the content of serum IL-4 was significantly increased,and the content of IL-8 was significantly decreased(P<0.05,P<0.01).The protein content and mRNA expression of JAK2 and STAT3 in colon tissue were significantly down-regulated,while the protein content and mRNA expression of SOCS1 were significantly go up(P<0.05,P<0.01).Conclusion:Electroacupuncture at each acupoint can improve the damage of colonic mucosa and reduce the inflammatory response.The therapeutic effect of Zusanli(ST36)is better than that of Tianshu(ST25),Dachangshu(BL25)and Shangjuxu(ST37).The mechanism may be related to the regulation of JAK2/STAT3/SOCS1 signaling pathway related proteins and inflammatory cytokines IL-4 and IL-8. 展开更多
关键词 ELECTROACUPUNCTURE different acupoints Acute colitis Inflammatory factors JAK2/STAT3/SOCS1 signaling pathway
下载PDF
The Influence of Depression on Different Age and Gender Groups in Bahawalpur
6
作者 Mehran Khan Muhammad Shahbaz +7 位作者 Tooba Waris Shoaib Yaseen Iqra Afzal Emaan Khadim Sawera Usman Muhammad Ismail Shah Sulaiman Aslam Zafar Iqbal 《Journal of Clinical and Nursing Research》 2024年第7期196-207,共12页
In Bahawalpur,a cross-sectional study assessed depression prevalence across age and gender groups,involving 442 participants from diverse socioeconomic backgrounds and settings.Utilizing the PHQ9 questionnaire,84%were... In Bahawalpur,a cross-sectional study assessed depression prevalence across age and gender groups,involving 442 participants from diverse socioeconomic backgrounds and settings.Utilizing the PHQ9 questionnaire,84%were found to meet depression levels.The findings revealed a higher incidence in females(88%)than males(79%),with the greatest disparity among young adults,particularly young women,due to factors like academic pressure and financial stress.School children had the lowest depression rates(68%),possibly due to better immunity.Elderly individuals exhibited more severe depression,likely related to aging and domestic challenges.The study’s findings highlight a significant variation in depression severity across different demographic groups,with an overall higher incidence in women.The research underscores the necessity for targeted mental health resources and interventions tailored to the specific needs of each demographic group.It also points to the importance of addressing academic and socioeconomic stressors to mitigate depression,particularly among young women.While the study provides valuable insights,it relies on self-reported data,which may introduce bias.Therefore,future research should include clinical assessments to validate these findings and ensure a more accurate representation of depression within the community. 展开更多
关键词 Influence DEPRESSION different age Gender groups Bahawalpur
下载PDF
Scientific connotation of “treating different diseases with the same method” from the perspective of metabolic-immune dysregulation in inflammation-mediated carcinogenesis of digestive organs
7
作者 Xia Ding Yunze Liu +2 位作者 Ruilin Wang Hong Shen Qi Wang 《Journal of Traditional Chinese Medical Sciences》 CAS 2023年第1期3-9,共7页
Inflammation-mediated carcinogenesis develops in the context of chronic inflammation and is a significant cause of cancer within the digestive system.In the chronic inflammation microenvironment,the metabolic activity... Inflammation-mediated carcinogenesis develops in the context of chronic inflammation and is a significant cause of cancer within the digestive system.In the chronic inflammation microenvironment,the metabolic activity of tissue cells undergoes extensive changes,which interfere with the normal function of immune cells.Dysregulation of cell metabolism and immune function has been identified as a key factor contributing to inflammation-mediated carcinogenesis within the major digestive organs,such as the stomach,liver,and colorectum.This metabolic-immune imbalance also corresponds to traditional Chinese medicine(TCM)theories of“yin-yang disharmony”and“disharmony between Ying-nutrients and Wei-defense.”The metabolic-immune imbalance has also been regarded as the key factor supporting“treatment of different diseases with the same method”,in which the same approach is adopted in the treatment of different conditions.In the TCM treatment process,it is necessary to first identify TCM patterns and then apply the corresponding TCM to correct the dysregulated metabolic and immune function,thereby blocking the progression from inflammation to malignancy.Our study findings deepen the TCM understanding of metabolic-immune dysregulation and the relationship between metabolic-immune dysregulation,pattern identification,and treatment method.They also provide new insights for the treatment of inflammation-mediated carcinogenesis in major digestive organs and help us further explore the scientific connotation of the TCM strategy of“treating different diseases with the same method”. 展开更多
关键词 Inflammation-mediated carcinogenesis Treating different diseases with the same method Metaboliceimmune regulation Metabolism Immunity Digestive system
下载PDF
Exploring the scientific rationality of“Different dosage forms of the same prescription”base on Q-markers of pulvis and pill of Chuanxiong Chatiao Prescription
8
作者 Ying Liu Xiao-Fei Zhang +3 位作者 Dong-Yan Guo Bing-Tao Zhai Jun-Bo Zou Ya-Jun Shi 《TMR Modern Herbal Medicine》 2023年第3期10-24,共15页
Objective:To predict and analyze the potential Q-markers of Chuanxiong Chatiao Prescription,and the pharmacokinetic properties of pulvis and pills in vivo were studied,which provided a basis for the rational evaluatio... Objective:To predict and analyze the potential Q-markers of Chuanxiong Chatiao Prescription,and the pharmacokinetic properties of pulvis and pills in vivo were studied,which provided a basis for the rational evaluation of the phenomenon of“Different Dosage Forms of the Same Prescription”.Methods and Material:Q-markers analysis of Chuanxiong Chatiao Prescription based on the“Five Principles”(traceability and transmissibility,specificity,effectiveness,prescription compatibility and testability).The content determination method of Q-markers in Chuanxiong Chatiao Prescription was established by UPLC,and the content difference of Q-markers in the two dosage forms ware determined and compared.The Q-markers in rabbit plasma was determined by LC-MS/MS method,and the pharmacokinetic parameters of Q-markers in pulvis and pills were analyzed.Results:A total of 16 potential Q-markers from the“Five Principles”were used,nine components of tetramethylprazine,ferulic acid,glycyrrhizin,glycyrrhizic acid,luteolin,cimicifugoside,senkyunolideⅠ,isoimperatorin,nodakenin were identified as Q-markers of Chuanxiong Chatiao Presciption.The content of tetramethylprazine and other components in the pulvis form was found to be significantly higher than that in the pills,while the content of senkyunolideⅠwas lower than that in the pills,which may be related to the preparation process of the dosage form and the physicochemical properties of the components.Compared with pulvis,the Tmax and t_(1/2)of ferulic acid and other components in pills were significantly prolonged.To a certain extent,it can explain the classical theory of traditional Chinese medicine“Components in pulvis release quickly and take effect in fast-acting manner,while in pills release slowly and take effect in slow-acting”.Meanwhile,the Cmax and AUC0-t of tetramethylprazine and other components in pills were higher than those in pulvis,which showed unexpected pharmacokinetic characteristics,indicating the complexity of compounding and the importance of dosage form design.Conclusions:A method for the determination of Q-markers content was established by UPLC,which provide reference for the quality control of Chuanxiong Chatiao Prescription.In vivo studies have found the pharmacokinetic parameters indicate the absorption and distribution characteristics of pulvis and pills.However,it is also found that the release behavior of different components not only affected by the dosage form but also closely related to their own physical and chemical properties. 展开更多
关键词 Chuanxiong Chatiao Prescription Q-marker different doses forms of the same presciption PHARMACOKINETICS pulvis PILL
下载PDF
Study on the influence of side-blown airflow velocities on plasma and combustion wave generated from fused silica induced by combined pulse laser
9
作者 余昊 蔡继兴 +3 位作者 毛洪涛 王云鹏 李忆 李顺 《Plasma Science and Technology》 SCIE EI CAS CSCD 2024年第7期165-176,共12页
This study examines the impact of variations in side-blowing airflow velocity on plasma generation,combustion wave propagation mechanisms,and surface damage in fused silica induced by a combined millisecond-nanosecond... This study examines the impact of variations in side-blowing airflow velocity on plasma generation,combustion wave propagation mechanisms,and surface damage in fused silica induced by a combined millisecond-nanosecond pulsed laser.The airflow rate and pulse delay are the main experimental variables.The evolution of plasma motion was recorded using ultrafast time-resolved optical shadowing.The experimental results demonstrate that the expansion velocities of the plasma and combustion wave are influenced differently by the sideblowing airflow at different airflow rates(0.2 Ma,0.4 Ma,and 0.6 Ma).As the flow rate of the sideblow air stream increases,the initial expansion velocities of the plasma and combustion wave gradually decrease,and the side-blow air stream increasingly suppresses the plasma.It is important to note that the target vapor is always formed and ionized into plasma during the combined pulse laser action.Therefore,the side-blown airflow alone cannot completely clear the plasma.Depending on the delay conditions,the pressure of the side-blowing airflow,the influence of inverse Bremsstrahlung radiation absorption and target surface absorption mechanisms can lead to a phenomenon known as the double combustion waves when using a nanosecond pulse laser.Both simulation and experimental results are consistent,indicating the potential for further exploration of fused silica targets in the laser field. 展开更多
关键词 different airflow speeds PLASMA combustion wave different pulse delay surface damage
下载PDF
A Theoretical Analysis of the Acceleration and the Angular Momentum of the Universe
10
作者 Ardeshir Irani 《Journal of High Energy Physics, Gravitation and Cosmology》 CAS 2024年第1期101-105,共5页
The loss of Baryonic Matter through Black Holes from our spatial 3-D Universe into its 4th dimension as Dark Matter, is used along with the Conservation of Angular Momentum Principle to prove theoretically the acceler... The loss of Baryonic Matter through Black Holes from our spatial 3-D Universe into its 4th dimension as Dark Matter, is used along with the Conservation of Angular Momentum Principle to prove theoretically the accelerated expansion of the 3-D Universe, as has already been confirmed experimentally being awarded the 2011 Nobel Prize in Physics. Theoretical calculations can estimate further to indicate the true nature of the acceleration;that the outward acceleration is due to the rotation of the Universe caused by Dark Energy from the Void, that the acceleration is non-linear, initially increasing from zero for the short period of about a Million years at a constant rate, and then leveling off non-linearly over extended time before the outward acceleration begins to decrease in a non-linear fashion until it is matched by the gravitational attraction of the matter content of 4D Space and the virtual matter in 3-D Vacuum Space. m = m(4D) + m(Virtual). The rotation of our 3D Universe will become constant once all 3D matter has entered 4D space. As the 3-D Universe tries to expand further it will be pulled inward by its gravitational attraction and will then keep on oscillating about a final radius r<sub>f</sub> while it also keeps on oscillating at right angles to the radius r<sub>f</sub> around final angular velocity ω<sub>f</sub>, until it becomes part of the 4-D Universe. The constant value of the Angular Momentum of our Universe is L = . 展开更多
关键词 3-D Baryonic Matter 3-D Virtual Matter 4-D Dark Matter Non-Linear Acceleration Final Radius Final Angular Velocity Conservation of Angular Momentum Principle
下载PDF
The Substructure of Elementary Particles Demonstrated by the I-Theory
11
作者 H. H. Swami Isa Christophe Dumas 《Journal of High Energy Physics, Gravitation and Cosmology》 CAS 2024年第2期469-514,共46页
Present studies in physics assume that elementary particles are the building blocks of all matter, and that they are zero-dimensional objects which do not occupy space. The new I-Theory predicts that elementary partic... Present studies in physics assume that elementary particles are the building blocks of all matter, and that they are zero-dimensional objects which do not occupy space. The new I-Theory predicts that elementary particles do indeed have a substructure, three dimensions, and occupy space, being composed of fundamental particles called I-particles. In this article we identify the substructural pattern of elementary particles and define the quanta of energy that form each elementary particle. We demonstrate that the substructure comprises two classes of quanta which we call “attraction quanta” and “repulsion quanta”. We create a model that defines the rest-mass energy of each elementary particle and can predict new particles. Lastly, in order to incorporate this knowledge into the contemporary models of science, a revised periodic table is proposed. 展开更多
关键词 I-theory I-Particle Causal Subtle Gross Quanta Attraction Quanta Repulsion Quanta Elementary Particles LEPTONS BOSONS Hadron Periodic Table Black Matter White Matter Red Matter Gravitation Strong Force Weak Force Quantum theory Heat Quantum Photon Neutrino
下载PDF
The Structure of Gravity Funnels and Stability Considerations of Matter in SI Units
12
作者 Tobias Bartusch 《Journal of High Energy Physics, Gravitation and Cosmology》 CAS 2024年第1期71-81,共11页
This article describes an extension of the theory of vortices to electromagnetic types with a start point from known fluid systems. From this, properties of gravity-generating objects (particles and black holes) can b... This article describes an extension of the theory of vortices to electromagnetic types with a start point from known fluid systems. From this, properties of gravity-generating objects (particles and black holes) can be derived, which can also describe their possible interior. This also leads to questions about stability, which are then addressed and ultimately lead to considerations of black holes and their possible internal structure. The results fit into the observable areas and can also be directly verified because they were analytically calculated in SI units. 展开更多
关键词 Black Hole Dark Matter Electromagnetic GRAVITY SINGULARITY VORTEX
下载PDF
Afforestation with an age-sequence of Mongolian pine plantation promotes soil microbial residue accumulation in the Horqin Sandy Land, China
13
作者 GUO Jingwen SONG Xueshu +2 位作者 WANG Xiao DU Zhangliu LU Sen 《Journal of Arid Land》 SCIE CSCD 2024年第4期567-579,共13页
Land use change affects the balance of organic carbon(C)reserves and the global C cycle.Microbial residues are essential constituents of stable soil organic C(SOC).However,it remains unclear how microbial residue chan... Land use change affects the balance of organic carbon(C)reserves and the global C cycle.Microbial residues are essential constituents of stable soil organic C(SOC).However,it remains unclear how microbial residue changes over time following afforestation.In this study,16-,23-,52-,and 62-year-old Mongolian pine stands and 16-year-old cropland were studied in the Horqin Sandy Land,China.We analyzed changes in SOC,amino sugar content,and microbial parameters to assess how microbial communities influence soil C transformation and preservation.The results showed that SOC storage increased with stand age in the early stage of afforestation but remained unchanged at about 1.27-1.29 kg/m2 after 52 a.Moreover,there were consistent increases in amino sugars and microbial residues with increasing stand age.As stand age increased from 16 to 62 a,soil pH decreased from 6.84 to 5.71,and the concentration of total amino sugars increased from 178.53 to 509.99 mg/kg.A significant negative correlation between soil pH and the concentration of specific and total amino sugars was observed,indicating that the effects of soil acidification promote amino sugar stabilization during afforestation.In contrast to the Mongolian pine plantation of the same age,the cropland accumulated more SOC and microbial residues because of fertilizer application.Across Mongolian pine plantation with different ages,there was no significant change in calculated contribution of bacterial or fungal residues to SOC,suggesting that fungi were consistently the dominant contributors to SOC with increasing time.Our results indicate that afforestation in the Horqin Sandy Land promotes efficient microbial growth and residue accumulation in SOC stocks and has a consistent positive impact on SOC persistence. 展开更多
关键词 soil organic matter stand age biomarker amino sugars microbial residues
下载PDF
Straw mulching alters the composition and loss of dissolved organic matter in farmland surface runoff by inhibiting the fragmentation of soil small macroaggregates
14
作者 Shanshan Cai Lei Sun +7 位作者 Wei Wang Yan Li Jianli Ding Liang Jin Yumei Li Jiuming Zhang Jingkuan Wang Dan Wei 《Journal of Integrative Agriculture》 SCIE CAS CSCD 2024年第5期1703-1717,共15页
Straw mulching is a widespread practice for reducing the soil carbon loss caused by erosion.However,the effects of straw mulching on dissolved organic matter(DOM)runoff loss from black soil are not well studied.How st... Straw mulching is a widespread practice for reducing the soil carbon loss caused by erosion.However,the effects of straw mulching on dissolved organic matter(DOM)runoff loss from black soil are not well studied.How straw mulching affects the composition and loss of runoff DOM by changing soil aggregates remains largely unclear.Here,a straw mulching treatment was compared to a no mulching treatment(as a control)on sloping farmland with black soil erosion in Northeast China.We divided the soil into large macroaggregates(>2 mm),small macroaggregates(0.25-2 mm),and microaggregates(<0.25 mm).After five rain events,the effects of straw mulching on the concentration(characterized by dissolved organic carbon(DoC)and composition(analyzed by fluorescence spectroscopy)of runoff and soil aggregate DOM were studied.The results showed that straw mulching reduced the runoff amount by 54.7%.Therefore,although straw mulching increased the average DOc concentration in runoff,it reduced the total runoff DOM loss by 48.3%.The composition of runoff DOM is similar to that of soil,as both contain humic-like acid and protein-like components.With straw mulching treatment,the protein-like components in small macroaggregates accumulated and the protein-like components in runoff declined with rain events.Fluorescence spectroscopy technology may help in understanding the hydrological paths of rain events by capturing the dynamic changes of runoff and soil DOM characteristics.A variation partitioning analysis(VPA)indicated that the DOM concentration and composition of microaggregates explained 68.2%of the change in runoff DOM from no mulching plots,while the change in runoff DOM from straw mulching plots was dominated by small macroaggregates at a rate of 55.1%.Taken together,our results demonstrated that straw mulching reduces the fragmentation of small macroaggregates and the loss of microaggregates,thus effecting DOM compositions in soil and reducing the DOM loss in runoff.These results provide a theoretical basis for reducing carbon loss in sloping farmland. 展开更多
关键词 dissolved organic matter black soil surface runoff AGGREGATES fluorescence spectrum
下载PDF
A Many Worlds Interpretation of the Dark Universe
15
作者 Richard Douglas Bateson 《Journal of High Energy Physics, Gravitation and Cosmology》 CAS 2024年第2期828-835,共8页
In this paper, we discuss a Many Worlds Interpretation (MWI) of Dark Energy and Dark Matter. The universe is viewed cosmologically as a fermionic fluid with a hydrostatic pressure from “Zitterbewegung”, the quantum ... In this paper, we discuss a Many Worlds Interpretation (MWI) of Dark Energy and Dark Matter. The universe is viewed cosmologically as a fermionic fluid with a hydrostatic pressure from “Zitterbewegung”, the quantum “zig-zagging” of Dirac particles. At each point in space-time, the pressure from all possible velocity states existing in the Many Worlds sums to provide a dark energy. This provides a ratio of matter energy to pressure energy close to that observed experimentally. Visible matter is the matter observed or measured in a particular velocity state and dark matter is then considered as the unobserved fermion contributions from different orthogonal spatial directions. 展开更多
关键词 Dark Energy Dark Matter Many Worlds
下载PDF
Biogeochemistry of sedimentary organic matter in the Yongjiang River estuary in the southern part of Hangzhou Bay,China,since the Late Pleistocene
16
作者 Dongqin HUANG Xiaolong LI +6 位作者 Zilong LI Pei Sun LOH Jianxiong HU Jianfang CHEN Yuan-Pin CHANG Chin-Wen YANG Qin GAO 《Journal of Oceanology and Limnology》 SCIE CAS CSCD 2024年第3期772-786,共15页
A sediment core(YJK19-02)collected from the southern outlet of Hangzhou Bay near the Yongjiang River estuary in East China was analyzed for grain size,lignin,bulk elemental composition,stable carbon isotope,and rare e... A sediment core(YJK19-02)collected from the southern outlet of Hangzhou Bay near the Yongjiang River estuary in East China was analyzed for grain size,lignin,bulk elemental composition,stable carbon isotope,and rare earth elements(REEs)to determine the sources and diagenesis of sedimentary organic matter(OM)of the estuary and adjacent areas since the Late Pleistocene.δ^(13)C values(-24.80‰–-23.60‰),total organic carbon/total nitrogen(TOC/TN)molar ratios(8.00–12.14),and light rare earth element/heavy rare earth element ratios(LREE/HREE=8.34–8.91)revealed the predominance of terrestrial sources of OM,mainly from the Changjiang(Yangtze)River.The lignin parameters of syringyl/vanillyl(S/V=0.20–0.73)and cinnamyl/vanillyl(C/V=0.03–0.19)ratios indicate the predominance of nonwoody angiosperms,and the vanillic acid/vanillin ratios[(Ad/Al)_(V)=0.32–1.57]indicate medium to high degrees of lignin degradation.An increasing trend ofΛ(total lignin in mg/100-mg OC)values from ca.14500 a BP to ca.11000 a BP reflected the increase in temperature during the Late Pleistocene.However,a time lag effect of temperature on vegetation abundance was also revealed.The relatively higher and stableΛvalues correspond to the higher temperature during the mid-Holocene from ca.8500 a BP to ca.4500 a BP.Λvalues decreased from ca.4000 a BP to the present,corresponding to historical temperature fluctuations during this time.Our results show that the vegetation abundance in the Yongjiang River Basin since the Late Pleistocene was related to the temperature fluctuation duo to climate change. 展开更多
关键词 Yongjiang River estuary sedimentary organic matter LIGNIN environmental change Late Pleistocene
下载PDF
Effect of thermal maturation and organic matter content on oil shale fracturing
17
作者 Fatemeh Saberi Mahboubeh Hosseini‑Barzi 《International Journal of Coal Science & Technology》 EI CAS CSCD 2024年第2期16-34,共19页
The Pabdeh Formation represents organic matter enrichment in some oil fields,which can be considered a source rock.This study is based on the Rock–Eval,Iatroscan,and electron microscopy imaging results before and aft... The Pabdeh Formation represents organic matter enrichment in some oil fields,which can be considered a source rock.This study is based on the Rock–Eval,Iatroscan,and electron microscopy imaging results before and after heating the samples.We discovered this immature shale that undergoes burial and diagenesis,in which organic matter is converted into hydro-carbons.Primary migration is the process that transports hydrocarbons in the source rock.We investigated this phenomenon by developing a model that simulates hydrocarbon generation and fluid pressure during kerogen-to-hydrocarbon conversion.Microfractures initially formed at the tip/edge of kerogen and were filled with hydrocarbons,but as catagenesis progressed,the pressure caused by the volume increase of kerogen decreased due to hydrocarbon release.The transformation of solid kerogen into low-density bitumen/oil increased the pressure,leading to the development of damage zones in the source rock.The Pabdeh Formation’s small porethroats hindered effective expulsion,causing an increase in pore fluid pressure inside the initial microfractures.The stress accumulated due to hydrocarbon production,reaching the rock’s fracture strength,further contributed to damage zone development.During the expansion process,microfractures preferentially grew in low-strength pathways such as lithology changes,laminae boundaries,and pre-existing microfractures.When the porous pressure created by each kerogen overlapped,individual microfractures interconnected,forming a network of microfractures within the source rock.This research sheds light on the complex interplay between temperature,hydrocarbon generation,and the development of expulsion fractures in the Pabdeh Formation,providing valuable insights for understanding and optimizing hydrocarbon extraction in similar geological settings. 展开更多
关键词 Oil shale MICRofRACTURE Hydrocarbon generation Organic matter thermal maturation Primary migration
下载PDF
Hard life for sons in the nest?Sex-dependent offspring mortality in Great Tits in urban and forest areas
18
作者 Nora Agh Henriett Anna Dalvári +2 位作者 Krisztián Szabó Ivett Pipoly András Liker 《Avian Research》 SCIE CSCD 2024年第1期91-97,共7页
Sex-biased mortality can occur in birds during development,for example due to sexual differences in energy requirement and/or environmental sensitivity,or the effects of sex hormones or sex differences in the expressi... Sex-biased mortality can occur in birds during development,for example due to sexual differences in energy requirement and/or environmental sensitivity,or the effects of sex hormones or sex differences in the expression of mutations linked to sex chromosomes.The extent of sex-bias in mortality may also be related to environmental conditions that influence offspring development and survival.Urban areas often provide poorer conditions for nestling development resulting in higher offspring mortality compared to natural areas,which may accelerate sex differences in offspring mortality in cities.To test this hypothesis,we examined the sex ratio of dead offspring in Great Tits(Parus major),using 427 samples of unhatched eggs and dead nestlings collected in two urban and two forest sites between 2013 and 2019.The ratio of males in the whole sample of dead offspring(56.9%)was significantly higher than expected by an 1:1 ratio,and the strongest sex biases were detected in urban areas(57.6%males)and in young nestlings(<14 days old,59.0%males).However,the sex ratios of dead offspring did not differ significantly among study sites and between offspring developmental stages.29.3%of unhatched eggs contained a visible embryo,and the proportion of embryo-containing unhatched eggs did not differ significantly between urban and forest study sites.These results suggest male-biased offspring mortality in Great Tits,and highlight the need of large datasets to detect subtle differences between habitats and developmental stages. 展开更多
关键词 Great Tit URBANIZATION Nestling mortality Sex related differences
下载PDF
Particle size characterization and sources of sediments in the Uzhumqin sand dunes
19
作者 ZHANG Hao LIU Yang +3 位作者 DANG Xiaohong MENG Zhongju LI Shuangli GAO Yong 《Journal of Mountain Science》 SCIE CSCD 2024年第8期2631-2645,共15页
Sediment constitutes the fundamental basis for forming and evolving aeolian geomorphology.The characteristics of sediment particle size offer insights into the development and evolution of sandy terrain,making their s... Sediment constitutes the fundamental basis for forming and evolving aeolian geomorphology.The characteristics of sediment particle size offer insights into the development and evolution of sandy terrain,making their study critical to understanding aeolian geomorphology and sand control.In this study,we combined high-density collection of surface sediments in the Uzhumqin sand dunes and GIS spatial analysis to analyze the particle size parameters and changes in the spatial distribution of surface sediments in this region.In addition,we used an end-member analysis to identify the potential sources of the sediments.The results showed that surface sediments in the Uzhumqin sand dunes had distinct spatial distributions.Medium and coarse grain sands dominated the sediments in the dunes,and the mean grain size and the sorting coefficient generally increased along the prevailing wind direction,with high values in individual areas related to factors such as material sources and vegetation cover.Skewness was strongly influenced by factors such as landform change and human activity,and spatial variability became more complex.Kurtosis and the soil fractal dimension showed generally decreasing trends along the prevailing wind direction.With dune fixation,the contents of clay and powder particles in the soil increased;the mean particle size,the sorting coefficient,and the fractal dimension of the soil gradually increased,and the skewness and kurtosis gradually decreased.The end-member analysis results indicated the existence of five end-members(EM)in the dune sediments.EM 1 was a mixed component of wind-deposited fine sands and nearby fluvial sediments.EM 2 was the main component of sediments in the study area and was the result of sorting lake sediments by wind action and by the local topography.EM 3 may be a product of river flood deposition.EM 4 and EM 5 had coarser grain sizes.EM 4 was a lake-phase sediment product influenced by topographic and vegetation cover factors,and EM 5 was primarily a river and lake sediment product modified by weathering.The sediment particle size results from the study area indicate that the sediment in the sandy region is generally coarse due to multiple factors,including topography,climate,hydrology,and human activity.Sandy material in the study area originated from nearby,with very little sand being transported from long distances. 展开更多
关键词 SEDIMENT Particle size Spatial differences End-member analysis Uzhumqin sand dunes
下载PDF
Using Natural Radionuclides to Trace Sources of Suspended Particles in the Lower Reaches of the Yellow River
20
作者 ZHANG Han BURNETT CWilliam +5 位作者 ZHANG Xiaojie ZHAO Shibin YANG Disong NAN Haiming YU Zhigang XU Bochao 《Journal of Ocean University of China》 CAS CSCD 2024年第1期99-108,共10页
Natural radionuclides are powerful tools for understanding the sources and fate of suspended particulate matter(SPM).Particulate matter with different particle sizes behaves differently with respect to adsorption and ... Natural radionuclides are powerful tools for understanding the sources and fate of suspended particulate matter(SPM).Particulate matter with different particle sizes behaves differently with respect to adsorption and desorption.We analyzed the activi-ties and distribution characteristics of multiple natural radionuclides(238U,226Ra,40K,228Ra,7Be and 210Pbex)on size-fractionated SPM at the Lijin Hydrographic Station(Huanghe or Yellow River)every month over a one-year period.Results showed that medium silt(16–32µm)was the main component.As expected,the activity of each radionuclide decreased with an increase of particle size.We examined the sources of SPM with different particle sizes using activity ratios of 226Ra/238U,228Ra/226Ra,40K/238U and 7Be/210Pbex,and concluded that SPM with different particle sizes originated from different sources.Our results indicate that fine SPM(<32µm)was mainly from the erosion of soil along the lower reaches of the Yellow River,while coarse SPM(>32µm)was mainly derived from resuspension of riverbed sediment.During high runoff periods,the concentration of SPM increased significantly,and the pro-portion of fine particles originating upstream increased.Naturally occurring radioactive isotopes,especially on size-fractionated par-ticles,are therefore seen as useful tracers to understand the sources and behaviors of riverine particles transported from land to sea. 展开更多
关键词 the Yellow River suspended particulate matter size-fractions radionuclides sediment sources water elutriator
下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部