Search

Low permeability reservoir is affected by sand body distribution, reservoir fracturing, and strong inter-layer heterogeneity and other factors [1]. After water breakthrough, water cut rises rapidly, oil production capacity declines rapidly, and it is difficult to stabilize oil production. In order to slow down oil production decline, the liquid production increasing method of the Yan60-1 well area is studied. The research on liquid production increasing technology is carried out by means of theoretical curve [2], numerical simulation and balance diagram of injection-production pressure [3]. Then the reasonable liquid production increasing time, amplitude and method of well field is determined to guide the adjustment of water injection development in low permeability reservoir.

Stimulated Raman scattering (SRS) is a major limiting factor for better performance of high-power fiber lasers. Several spectral filtering methods have been used for Raman suppression, among which long period fiber grating (LPFG) is relatively simple and effective due to its all-fiber structure and broadband rejection properties. Here, a broadband, low insertion loss and low thermal effect LPFG is easily fabricated using CO2 laser by galvanometer scanning, then is used for SRS suppression within a high-power fiber oscillator for the first time. Results show that a maximum SRS suppression ratio of ~16 dB was achieved and the extractable Raman-free output power was increased by about 13% with the insertion of LPFG. This work has demonstrated a potentially applicable method for Raman suppression in high-power fiber oscillators.

The average output power of fiber laser oscillators can stabilize in very high levels reaching kW within the recent years. However, a further scaling is limited due to some nonlinear effects, one of which is simulated Raman scattering (SRS). Here we propose a CO2 laser pulse inscribed transmission long period fiber grating (LPFG) in large mode area (LMA) fiber and employ it within a fiber laser oscillator to mitigate SRS. The wavelength of LPFG is designed to match the peak of SRS gain spectrum. By inserting the LPFG before the output coupling FBG (OC-FBG) of the oscillator, an efficient mitigation of SRS is observed. LPFGs represent a highly cost-effective fiber structure with potential for SRS suppession in high power fiber laser systems.

Stage-specific gene expression governs metamorphosis of the silkworm, Bombyx mori. B. mori wing cuticle protein gene 4 (BmWCP4) is an essential gene for wing disc development expressed specifically during pupation. BmWCP4 transcription is suppressed at the larval stage by unknown mechanisms, which we sought to elucidate here. Bioinformatics analysis predicted seven potential Forkhead box (Fox) cis-regulatory elements (CREs) in the BmWCP4 promoter region, and we found that Fox CRE6 contributes to suppression of BmWCP4 expression. Electrophoretic mobility shift (EMSA) and DNA pull-down assays revealed that BmFoxA suppressed activity at the BmWCP4 promoter by specifically binding to the Fox CRE6. The expression level of BmFoxA in the wing discs was higher during the larval stage than at the pupal stage. In contrast, expression of another transcription factor, BmSAGE, increased over the course of development. Of note, the hormone 20-hydroxyecdysone (20E), which governs molting in insects, suppressed BmFoxA expression in the wing discs and up-regulated that of BmSage. EMSA and cell co-transfection assays indicated that BmSAGE interacted with BmFoxA and suppressed its binding to the Fox CRE6, thereby releasing BmFoxA-mediated suppression of BmWCP4. In summary, higher BmFoxA expression during the larval stage suppresses BmWCP4 expression by binding to the Fox CRE6 on the BmWCP4 promoter. During metamorphosis, BmSAGE forms a complex with BmFoxA to relieve this repression, initiating BmWCP4 expression. Taken together, this study reveals a switchlike role for BmFoxA in regulating BmWCP4 expression and provides new insights into the regulatory regulation of wing disc development in insects.

BACKGROUND Scientists placed less aligned emphasis on naming the emerging SARS-CoV-2 variants, and yet a holistic standard nomenclature scheme for viral variants remains to be fleshed out and full-fledged. In the context of the COVID-19 infodemic, the global profusion of stigmatizing geographical names for those variants have found their way into daily communication at the cost of social stigma in the wake of COVID-19 pandemic. OBJECTIVE This study examines why standard nomenclature for SARS-CoV-2 variants rises to the occasion, as well as the rational principles of a curated nomenclature framework for viral variants and abbreviations. METHODS In the scientometric analysis experiment, we retrieved the metadata of 693 articles from the Web of Science Core Collections between 30 December 2019 and 25 March 2021, to demonstrate the stigmatizing geographical names of SARS-CoV-2 variants in the scientific sphere. In the global online news coverage experiments, we examined the compiled global online news volumes and emotional tones between December 2019 and May 2021 to demonstrate the emotional polarity of the contextualizing stigma over time. The results could cover 65 multilingual textual and visual narratives by leveraging the capacity of GDELT’s machine translation and neural network image recognition. In the genomic epidemiology experiment, we reproduced the genomic epidemiology of evolutionary SARS-CoV-2 exemplified by 3955 genomes from the ongoing COVID-19 pandemic based on the Nextstrain database. RESULTS The results of the scientometric analysis show that some racial stereotypes of SARS-CoV-2 variants like “UK variant” have found their way in scientific literature. The global online news coverage experiments also indicate that such flawed word-blends are widely professed in news outlets in 65 different languages. After December 2020, those contextualizing stigmas in textual and visual narratives with extremely negative tones are fuelling the current COVID-19 infodemic in up to 100 countries. The genomic epidemiology experiment exemplifies that simply distinguishing variants based on the presumed locations would introduce new confusions in both the scientific sphere and the public. CONCLUSIONS The surveys suggest that current collective propensities to contextualizing stigmas would result in social costs, without a one-size-fits-all nomenclature framework for SARS-CoV-2 variants. Such urgent concern that evoked by multiple nomenclature conventions needs coordinated global responses. As an integral component of preparedness, we propose the rational principles of a standard nomenclature framework for viral variants and abbreviations based on heuristic introspection of naming practices for viral variants.

We demonstrate here a method for the online temperature measurement of the output-coupling fiber Bragg grating (FBG) in a high power fiber oscillator by a superimposed FBG, which is used as the output-coupling FBG and the temperature monitor simultaneously. The experimental results verify the feasibility of this method.

In order to study the mechanism of abnormal deoxyribonucleic acid methylation in the process of lung cancer in rats, Wistar rats are used as the research object. The lung cancer model of rats is established by bronchial perfusion of carcinogens. Hematoxylin-eosin staining is used to observe the pathological changes of lung tissue in rats. The overall methylation level of genome is analyzed by immunohistochemistry, and the methylation status is detected by methylation specific polymerase chain reaction. The results show that the nuclei of normal bronchial epithelial cells are brown and yellow uder optical microscope. With the development of carcinogenesis, the staining gradually fades to light yellow in the infiltrating nuclei of cancer cells. Compared with normal bronchial epithelial cells, the optical density and integrated optical density values of 5-mC immunohistochemistry decrease. The methylation frequency of p16 gene in atypical hyperplasia, carcinoma in situ and invasive cancer tissues is significantly higher than that in normal and proliferative tissues. The methylation frequency of p57 gene is significantly higher in carcinoma in situ and invasive tissues than in normal and proliferative tissues. Abnormal methylation-mediated down-regulation of p16 and p57 gene transcription may be an important molecular biological event in carcinogenesis of lung cancer rats induced by carcinogens. There are still some shortcomings in the research process, but the results of the study still provide some reference and guidance for exploring more precise mechanism in the future. Therefore, this study is a significant research topic.

We measured the temperature of a single point using a uniform fiber Bragg grating (FBG) for the first time. A quasi- Gaussian temperature distribution pattern was achieved by heating at the midpoint of FBG, then the spectral characteristics, mainly including the central wavelength and amplitude of the resonance peaks were investigated in detail. Results show that the attenuation of each peaks accords well with the theoretical predictions, so the temperature of midpoint can be demodulated by the analysis of transmission spectra.

Micro-blog has become the main distribution center of public opinion. Therefore, how to mine hot topics from microblog has become a hot topic. However, microblogs are mostly short texts and contain a large number of invalid information, which significantly increases the difficulty of hot topic detection. On the other hand, micro-blog includes text, pictures and comment information, which greatly enriches the diversity of information. Therefore, this paper proposed a new method, which applies deep learning to image understanding. Image content is interpreted as analyzable text semantic information combined with comments to enrich short text information. Experimental results show the effectiveness of the proposed method, and better experimental results are obtained compared with other methods.

In this paper, we propose and demonstrate a novel method for the suppression of SBS in optical fibers using a tilted fiber Bragg grating (TFBG). We designed and fabricated a matched TFBG by using an excimer laser and phase mask in single mode fibers according to the operating wavelength of the fiber laser and the tiny frequency shift of SBS. Experimental results demonstrate that TFBGs can suppress the backward-propagating Stokes light caused by SBS to protect the whole system and improve the stable output power, which is very useful for power scaling of high-power narrow-bandwidth all-fiber laser in the future.

C-type lectins (CTLs) recognize various glycoconjugates through carbohydrate recognition domains (CRDs) and they play important roles in immune responses. In this study, comparative genomic analysis of CTLs were performed in 7 holometabolous species. CTL-S1 to S8 and CTL-X1 to X4 orthologous groups existed in the 7 species, while CTL-X5 group with dual-CRD, CTL-S11 group with triple-CRD, CTL-S9 group with a long C-terminus and Lepidopteran specific CTL-S10 group were not conserved. SliCTL-S12 to S14 cluster was only present in Spodoptera litura, and CTL-S genes were expanded on chromosomes 2 L and 2 R in Drosophila melanogaster. Most IMLs were clustered into three groups and the numbers of IMLs vary among species due to gene duplications. D. melanogaster specific CTLs and Lepidopteran IMLs within each of the three groups evolved more rapidly with higher dN/dS ratios. Two CRDs in IMLs clustered into two clades, with conserved Cys4-Cys5 and Cys1-Cys2 bonds in the first and second CRDs, respectively. The CTL-S and CTL-X family members in S. litura were mainly expressed in the fat body of 5th but not 6th instar larvae, and responded differently to S. litura nucleopolyhedrovirus (SpltNPV) and Nomuraea rileyi infection. The transcription levels of SliCTLs that expressed in fat body but not highly expressed in hemocytes were decreased at the middle and late stages of SpltNPV infection, and the mRNA levels of SliCTLs highly or specifically expressed in hemocytes were mainly decreased by SpltlNPV, N. rileyi and Bacillus thuringiensis infection. These results provide valuable information for further exploration of CTL functions in host-pathogen interaction.

Here, the influence of rejection bandwidth of chirped and tilted fiber Bragg gratings on Raman suppression is studied in a 5 kilowatt-level direct LD pumped MOPA fiber laser. A better suppression could be achieved with a broader-band CTFBG, which is quite useful for further power scaling. © 2020 The Author(s)

We report here the effective suppression of stimulated Raman scattering (SRS) in a LD directly pumped 5 kW 1080 nm fiber amplifier using chirped and tilted fiber Bragg gratings (CTFBGs). The CTFBGs are carefully designed and fabricated to match the Raman gain spectrum, and experimental results show that the SRS suppression ratio is about 27.5 dB at 5 kW.

Long period fiber grating (LPFG) can be used as a band rejection component, providing a potential effective way for Stimulated Raman scattering (SRS) suppression in high power fiber laser. Here, an improved CO2 laser scanning system with a galvanometer is built up for fabrication of LPFGs, which greatly improves the speed and consistency of grating inscribing. The characteristics of the manufactured LPFG is measured in detail, then a direct laser diode pumped 5 kW-level fiber amplifier system is established to test the validity of the LPFGs for Raman suppression for the first time. Experimental results show that the SRS suppression ratio is about 14 dB at 5.1 kW with the LPFG being inserted between the seed and the amplifier stage, meanwhile the effective output signal laser power is increased. In contrast to the ultraviolet laser exposed band rejection components, such as chirped and tilted fiber Bragg grating (CTFBGs), this type of LPFG does not need photosensitive fibers, annealing treatment and has a much lower thermal effect, which is very useful for high-power fiber lasers applications.

A segmented long period fiber grating (LPFG)-based torsion sensor with both high sensitivity and ability to discriminate torsion direction is proposed and experimentally investigated. The sensor is made up of three spatial orthogonal short LPFGs by using a CO2 laser notched method. Experimental results show that the torsion sensitivities can reach −0.54 and 0.33 dB/(rad/m) in dip depth and 0.30 and −0.14 nm/(rad/m) in resonance wavelength for clockwise and counterclockwise, respectively, in a single polarization state. Torsion rate and torsion direction can be measured simultaneously by the sensor. Moreover, the temperature sensitivity of the sensor has been determined as 0.067 nm/°C. Therefore, the proposed segmented-LPFG would have great potential applications in engineering and fiber sensors.

A novel long-period fiber grating via periodically embedding no-core fiber (NCF) has been achieved. The 11-period SMF-NCF-SMF-long period fiber grating (SNS-LPG) can exhibit an extremely high loss resonant dip (>20 dB). Theoretical analysis shows good agreement with the measured transmission spectrum. We investigated both refractive index and temperature sensitivity of SNS-LPG. The fabricated sensor achieve an average wavelength sensitivity of 141.837 nm/RIU in the range of 1.333–1.400 RIU, and exhibit lower temperature sensitivity (−6.43 pm/ °C and 0.005 dB/ °C).

A highly sensitive curvature sensor made of a novel long period fiber grating (LPFG) is presented and experimentally demonstrated. It is constructed by splicing multiple single mode fibers (SMFs) and multi-mode fibers (MMFs) alternately (MS/MA). The measurement result shows that it has a high sensitivity of −22.4 nm/m−1 in the range from 0.223 m−1 to 4.358 m−1. It can measure curvature on all direction due to the symmetric structure. The proposed sensor was also insensitive to the temperature, whose temperature sensitivity was around −0.015 nm/°C in the range from 40 °C to 200 °C. The advantages of high curvature sensitivity and low temperature sensitivity make it has a great potential to measure curvature in practical application with high resolutions.

We propose the design of a high-power fiber oscillator with chirped and tilted fiber Bragg gratings (CTFBGs) to suppress the stimulated Raman scattering within the fiber cavity and in the delivery fibers. A high-power single-mode fiber oscillator system was constructed for demonstration. With a CTFBG inserted into the fiber cavity, obvious Raman suppression was observed and the output signal laser power increased by ∼7%. With a CTFBG inserted between the oscillator and the delivery fibers, a maximum Raman suppression ratio of >20 dB was achieved, which implies a longer delivery distance for the same laser power level. By further improving the performance of CTFBGs, including lower inversion loss at signal wavelength, wider rejection bandwidth and deeper rejection depth, meanwhile optimizing the positions of CTFBGs, better Raman suppression could be obtained, which is significant for the further power scaling and delivery distance increasing of high-power fiber oscillators.

A novel dual-use superimposed fiber Bragg grating (FBG) consisting of a normal FBG operating at 1.55 μm and a chirped FBG (CFBG) operating at 1.08 μm is fabricated and applied in a fiber laser oscillator. The 1.08 μm CFBG is used as a reflector of the fiber oscillator and the FBG is used as an in-core temperature on-line monitor of the laser simultaneously. According to the temperature characteristics of the FBG, the real-time inner temperature can be obtained by detecting the shift of the reflection spectrum. Experimental results have proved the effectiveness of the proposed temperature monitor, which can give the temperature inside a fiber laser comparing to the normal surface measurement techniques such as infrared (IR) camera. This paper provides a simple method to detect the local in-core temperature of fiber lasers, which is useful for investigations of high-power fiber lasers system.

The key remaining technological challenge to the realization of further power scaling for high-power fiber laser systems is overcoming the stimulated Raman scattering (SRS) effect. In past years, chirped and tilted fiber Bragg gratings (CTFBGs) have been demonstrated to be a simple and effective way to suppress SRS in high-power fiber amplifiers. However, the weak reflection at the Bragg wavelength could be strongly amplified, which not only limits the power and efficiency but also degrades the beam quality. We report here, for the first time to the best of our knowledge, the influence of the residual Bragg reflection of CTFBGs on SRS suppression in high-power fiber laser systems. Two groups of CTFBGs with different Bragg reflection wavelengths are fabricated and used for the comparison experiments. Test results show that the CTFBGs of longer Bragg wavelengths have a better suppression effect, in particular, at a higher power level. By further moving the Bragg wavelength of a CTFBG out of the Raman gain spectral range, a better suppression effect and a promotion in laser efficiency could be achieved, which is very useful for further power scaling.

A novel hybrid fiber Bragg grating (FBG) for simultaneous measurement temperature and strain is proposed. This sensor is fabricated by inscribing fusion splice joint between two types of fibers using excimer laser and phase mask. Due to the different characteristics of the two fibers, the two resonance peaks have different responses to temperature and strain, and both physical parameters can be demodulated by analyzing the central wavelength shifts. Practical measuring results show that the hybrid FBG proposed in this paper can precisely achieve simultaneous measurement of temperature and strain. This work provides a new scheme for multi-parameter simultaneous sensing.

We propose here a novel method for position fixing in the micron scale by combining the convolutional neural network (CNN) architecture and speckle patterns generated in a multimode fiber. By varying the splice offset between a single mode fiber and a multimode fiber, speckles with different patterns can be generated at the output of the multimode fiber. The CNN is utilized to learn these specklegrams and then predict the offset coordinate. Simulation results show that predicted positions with the precision of 2 μm account for 98.55%. This work provides a potential high-precision two-dimensional positioning method.

We have demonstrated here, to the best of our knowledge, for the first time the suppression of stimulated Raman scattering (SRS) in a monolithic fiber laser oscillator using chirped and tilted fiber Bragg gratings (CTFBGs). We designed and inscribed CTFBGs in large-mode-area (LMA) fibers according to the operating wavelength of the fiber laser oscillator. A maximum suppression ratio nearly 19 dB or 23 dB is achieved CTFBG insert before the OC grating or after the HR grating. By reducing the insertion loss and improving the transmission spectrum of the CTFBG, a promotion in laser efficiency could be achieved. This work provides a novel idea for SRS suppression in a high-power all-fiber oscillator system, which is very useful for the output power increasing of fiber oscillators.

The average power of fiber lasers has been scaled deeply into the kW regime in the past years. However, stimulated Raman scattering (SRS) is still a major factor limiting further power scaling. Here, we have demonstrated for the first time, to the best of our knowledge, the suppression of SRS in a half 10 kW tandem pumping fiber amplifier using chirped and tilted fiber Bragg gratings (CTFBGs). With specially self-designed and manufactured CTFBGs inserted between the seed laser and the amplifier stage, a maximum SRS suppression ratio of >15 dB in spectrum is observed with no reduction in laser efficiency. With one CTFBG, the effective output power is improved to 3.9 kW with a beam quality M2 factor of ∼1.7 from 2; with two CTFBGs, the effective laser power reaches 4.2 kW with an increasing ratio of 20% and an M2 factor of ∼1.8, and further power improvement is limited by the power and performance of the 1018 nm pump sources. This work provides an effective SRS suppression method for high-power all-fiber lasers, which is useful for further power scaling of these systems.

The transcription factor BmPOUM2 interacted with another transcription factor BmAbd-A to regulate the expression of the wing cuticle protein gene BmWCP4 in Bombyx mori. In this study, the binding domains and amino acids for the interaction between BmPOUM2 and BmAbd-A were reported. Two isoforms of BmPOUM2 were identified. The short isoform (BmPOUM2-S) lacks a 114-amino acid sequence containing a POU-homeodomain and a nuclear localization signal peptide (NLS), as compared to the full-length isoform (BmPOUM2). Both BmPOUM2 and BmPOUM2-S proteins bound to the BmAbd-A through the POU-specific domain. When the six amino acids (Lys166, Gly173, Gln176, Ser192, Glu200 and Asn208) that are highly conserved in POU family genes were mutated, BmPOUM2 did not bind to BmAbd-A. BmAbd-A interacted with BmPOUM2 by the homeobox domain or the LCR2 (low complexity region) domain. When seven amino acids (Phe156/248, His158/250, Ala175/263, Cys180/265, Glu190/268, Trp196/274 and Val214/289) that are shared in the homeobox and LCR2 domains were mutated, BmAbd-A did not bind to BmPOUM2. Overexpression of either BmPOUM2 or BmAbd-A or both increased the activity of BmWCP4 promoter in CHO cells. ChIP assay and EMSA showed that BmAbd-A protein bound to the Hox cis-regulatory element in the BmWCP4 promoter, while the BmPOUM2 bound to the nearby POU CRE. A model for the interaction and action of BmPOUM2 and BmAbd-A in regulation of the BmWCP4 expression is proposed.

At present, production split methods mainly include effective thickness method, formation coefficient method and dynamic equation split method. On account of various factors restriction, the applied results are unsatisfactory. In order to fully grasp the multilayer reservoir layering exploitation status, a new production split method is established by utilizing grey relational analysis based on traditional production split methods. The new method divides the influence factors of single layer production split into static geological factor and dynamic development factor. We confirm correlation degree weight of static geological factor and dynamic development factor by utilizing grey relational analysis, which synthetically considers various production split influence factors. And finally a new production split method is established. Through actual applied verification, the new method is accurate and widely adaptable, which provides a new idea for production split work.