The evolution of microbialite forms during the Early Triassic transgression: A case study in Chongyang of Hubei Province, South China

The widespread development of microbialites in shallow areas of the Tethys Ocean at the start of the Early Triassic reflects the deterioration of marine ecosystems in the aftermath of the extinction that marked the demise of the majority of Palaeozoic marine faunas. Here we present a study of the evolving microbialite forms and associated biotic assemblages of this pioneering microbialite interval from exposures at Chongyang, Hubei Province, China. This research provides a perspective on the effects of eustatic transgression on marine ecosystems as water depths increased at the beginning of Mesozoic, through the study of the changing forms, microfacies and distribution of microbialites. Microbialite forms evolved from stratiform stromatolites to a sequence of tabular thrombolites (with an intercalated layer of columnar stromatolites), followed by domical thrombolites that were overlain, in turn, by oolites. The stratiform stromatolites contain poorly preserved remains of calcified cyanobacteria, but microfossils with chambered structure can also be seen. Metazoan fossils increased from the base of the overlying tabular thrombolite, reflecting increasing biodiversity with deepening of seawater. The occurrence of columnar stromatolites within the tabular thrombolite may indicate a temporary sea-level shallowing. Foraminiferans and other metazoans are absent within the columnar stromatolites, but spherical cyanobacterial remains are extremely abundant. Well-preserved calcified cyanobacteria may reflect an absence of metazoan predation and/or carbonate supersaturation of seawater. As water deepened, domical thrombolites developed and the more complex seafloor relief created varied niches between and within the domes that harboured more ecologically diverse communities. During the process of transgression within the microbialite interval, carbon isotopes exhibit a negative relationship with biodiversity, implying that upwelling of anoxic deep-ocean water, if associated with the negative excursion of carbon isotope values, did not inhibit the diversification of benthic organisms at least on shallow carbonate platforms in the period immediately after the end-Permian mass extinction.This study was jointly supported by the National Natural Science Foundationof China (Grants No. 41730320 and No. 41572001) and the 111 project(B08030

A Multi-Pass Optically Pumped Rubidium Atomic Magnetometer with Free Induction Decay

A free-induction-decay (FID) type optically-pumped rubidium atomic magnetometer driven by a radio-frequency (RF) magnetic field is presented in this paper. Influences of parameters, such as the temperature of rubidium vapor cell, the power of pump beam, and the strength of RF magnetic field and static magnetic field on the amplitude and the full width at half maximum (FWHM) of the FID signal, have been investigated in the time domain and frequency domain. At the same time, the sensitivities of the magnetometer for the single-pass and the triple-pass probe beam cases have been compared by changing the optical path of the interaction between probe beam and atomic ensemble. Compared with the sensitivity of ~21.2 pT/Hz^(1/2) in the case of the single-pass probe beam, the amplitude of FID signal in the case of the triple-pass probe beam has been significantly enhanced, and the sensitivity has been improved to ~13.4 pT/Hz^(1/2). The research in this paper provids a reference for the subsequent study of influence of different buffer gas pressure on the FWHM and also a foundation for further improving the sensitivity of FID rubidium atomic magnetometer by employing a~polarization-squeezed light as probe beam, to achieve a sensitivity beyond the photo-shot-noise level.Comment: sensors,2022,22(19):759

Characterizing current noise of commercial constant-current sources by using of an optically-pumped rubidium atomic magnetometer

This paper introduces a method for characterizing the current noise of commercial constant-current sources(CCSs) using a free-induction-decay(FID) type optically-pumped rubidium atomic magnetometer driven by a radio-frequency(RF) magnetic field. We convert the sensitivity of the atomic magnetometer into the current noise of CCS by calibrating the coil constant. At the same time, the current noise characteristics of six typical commercial low-noise CCSs are compared. The current noise level of the KeySight Model B2961A is the lowest among the six tested CCSs, which is 36.233 0.022 nA / Hz1/2 at 1-25 Hz and 133.905 0.080 nA / Hz1/2 at 1-100 Hz respectively. The sensitivity of atomic magnetometer is dependent on the current noise level of the CCS. The CCS with low noise is of great significance for high-sensitivity atomic magnetometer. The research provides an important reference for promoting the development of high precision CCS, metrology and basic physics research.Comment: 7pages,7figure

Measuring magnetic field coil constants based on atomic magnetometry and fluxgate magnetometry

In a magnetic field detection system,to achieve high-sensitivity magnetic field measurement, it is necessary to use uniform magnetic field coils to provide a stable working environment, so the measurement of the magnetic field coilsconstant is of great significance. To accurately measure the magnetic field and compare the coil constant, we employed two different methods under good magnetic shielding conditions: the optically-pumped rubidium free-induction decay magnetometry and the fluxgate magnetometry. In terms of measuring coil constant, the optically-pumped rubidium FID magnetometer performs better than fluxgate magnetometer due to its high-sensitivity and good signal-to-noise ratio. We compare the magnetic field measured by the FID magnetometer with that of the fluxgate magnetometer and obtain a calibration factor of 0.9967. The calibration of fluxgate magnetometer with optically-pumped atomic magnetometer is realized. The method is simple and easy to operate for calibrating fluxgate magnetometer.Comment: 11 pages, 6 figure

Comparison and analysis of methods for measuring the spin transverse relaxation time of rubidium atomic vapor

The spin transverse relaxation time (T_2) of atoms is an important indicator for precision measurement. Several methods have been proposed to characterize the T_2 of atoms. In this paper, the T_2 of rubidium (Rb) atomic vapor in the same cell was measured using four measuring methods, namely spin noise spectrum signal fitting, improved free induction decay (FID) signal fitting, w_m-broadening fitting, and magnetic resonance broadening fitting. Meanwhile, the T_2 of five different types of Rb atomic vapor cells were measured and characterized. A comparative analysis visualizes the characteristics of the different measuring methods and the effects of buffer gas on T_2 of Rb. We theoretically and experimentally analyzed the applicability of the different methods, and then demonstrated that the improved FID signal fitting method provides the most accurate measurement because of the clean environment in which the measurements were taken. Furthermore, we demonstrated and qualitatively analyzed the relationship between the atomic number density and the T_2 of Rb. This work provides analytical insight in selecting atomic vapor cells, and may shed light on the improvement of the sensitivity of atomic magnetometers

An extensive anoxic event in the Triassic of the South China Block : a pyrite framboid study form Dajiang and its implications for the cause(s) of oxygen depletion

Water column oxygen deficiency has been considered as a potent driver of the extinction of marine benthos, and is a main feature of marine environments in the aftermath of the end-Permian mass extinction. The record of Permian-Triassic anoxia is more complex than previously thought, and is seen to vary between different palaeogeographic settings, but a full understanding is hindered by a paucity of evidence. During the Permian-Triassic interval the South China Block was located equatorially with Palaeotethys to the north and western Panthalassa to the south. This specific configuration provides a unique opportunity to compare the extent and duration of oxygen deficiency in Palaeotethys and Panthalassa under broadly similar climatic conditions. Sedimentary facies and pyrite framboid size-frequency distributions suggest that the oxygen-poor conditions became widespread across the shallow-marine carbonate platform of the South China Block immediately above the Permian-Triassic boundary and mass extinction level. Oxygen deficiency was most intense at the southern margin of the block where it met Panthalassa. Proposed drivers of the expansion of oxygen minimum zones into platform settings include enhanced terrigenous input and/or ocean stratification, or alternatively the upwelling of nutrient-rich deep ocean water. The former mechanisms are theoretically more likely to have operated in the relatively restricted Palaeotethys which was surrounded by ancient lands. In contrast, Panthalassa would likely have experienced stronger oceanic circulation and therefore be more susceptible to the effects of upwelling. Although variations in the record of the South China Block anoxic event might reflect local factors, the greater intensity of oxygen deficiency and a concomitant larger negative shift in carbonate carbon isotopes on its Panthalassan margin point to a key role for upwelling. This mechanism was likely a major driver of the Permian-Triassic global oceanic anoxic event, which itself was at least partly responsible for the ongoing inhospitable conditions and delayed recovery following the end-Permian extinction

Genome-scale analysis and comparison of gene expression profiles in developing and germinated pollen in Oryza sativa

<p>Abstract</p> <p>Background</p> <p>Pollen development from the microspore involves a series of coordinated cellular events, and the resulting mature pollen has a specialized function to quickly germinate, produce a polar-growth pollen tube derived from the vegetative cell, and deliver two sperm cells into the embryo sac for double fertilization. The gene expression profiles of developing and germinated pollen have been characterised by use of the eudicot model plant <it>Arabidopsis</it>. Rice, one of the most important cereal crops, has been used as an excellent monocot model. A comprehensive analysis of transcriptome profiles of developing and germinated pollen in rice is important to understand the conserved and diverse mechanism underlying pollen development and germination in eudicots and monocots.</p> <p>Results</p> <p>We used Affymetrix GeneChip^®Rice Genome Array to comprehensively analyzed the dynamic changes in the transcriptomes of rice pollen at five sequential developmental stages from microspores to germinated pollen. Among the 51,279 transcripts on the array, we found 25,062 pollen-preferential transcripts, among which 2,203 were development stage-enriched. The diversity of transcripts decreased greatly from microspores to mature and germinated pollen, whereas the number of stage-enriched transcripts displayed a "U-type" change, with the lowest at the bicellular pollen stage; and a transition of overrepresented stage-enriched transcript groups associated with different functional categories, which indicates a shift in gene expression program at the bicellular pollen stage. About 54% of the now-annotated rice F-box protein genes were expressed preferentially in pollen. The transcriptome profile of germinated pollen was significantly and positively correlated with that of mature pollen. Analysis of expression profiles and coexpressed features of the pollen-preferential transcripts related to cell cycle, transcription, the ubiquitin/26S proteasome system, phytohormone signalling, the kinase system and defense/stress response revealed five expression patterns, which are compatible with changes in major cellular events during pollen development and germination. A comparison of pollen transcriptomes between rice and <it>Arabidopsis </it>revealed that 56.6% of the rice pollen preferential genes had homologs in <it>Arabidopsis </it>genome, but 63.4% of these homologs were expressed, with a small proportion being expressed preferentially, in <it>Arabidopsis </it>pollen. Rice and <it>Arabidopsis </it>pollen had non-conservative transcription factors each.</p> <p>Conclusions</p> <p>Our results demonstrated that rice pollen expressed a set of reduced but specific transcripts in comparison with vegetative tissues, and the number of stage-enriched transcripts displayed a "U-type" change during pollen development, with the lowest at the bicellular pollen stage. These features are conserved in rice and <it>Arabidopsis</it>. The shift in gene expression program at the bicellular pollen stage may be important to the transition from earlier cell division to later pollen maturity. Pollen at maturity pre-synthesized transcripts needed for germination and early pollen tube growth. The transcription regulation associated with pollen development would have divergence between the two species. Our results also provide novel insights into the molecular program and key components of the regulatory network regulating pollen development and germination.</p

The application and research progress of anti-angiogenesis therapy in tumor immunotherapy

Tumor immunotherapy, as the focus of scientific research and clinical tumor treatment in recent years, has received extensive attention. Due to its remarkable curative effect and fewer side effects than traditional treatments, it has significant clinical benefits for the treatment of various advanced cancers and can improve cancer patient survival in the long term. Currently, most patients cannot benefit from immunotherapy, and some patients may experience tumor recurrence and drug resistance even if they achieve remission overcome. Numerous studies have shown that the abnormal angiogenesis state of tumors can lead to immunosuppressive tumor microenvironment, which affects the efficacy of immunotherapy. Actually, to improve the efficacy of immunotherapy, the application of anti-angiogenesis drugs to normalize abnormal tumor vessel has been widely confirmed in basic and clinical research. This review not only discusses the risk factors, mechanisms, and effects of abnormal and normalized tumor angiogenesis state on the immune environment, but summarizes the latest progress of immunotherapy combined with anti-angiogenic therapy. We hope this review provides an applied reference for anti-angiogenesis drugs and synergistic immunotherapy therapy