The paper presents the change in grain-size composition of lignite under cyclic freezing-thawing (FTC) and wetting-drying (WDC). The article shows that in the spring and autumn periods the lignites can be subjected to...The paper presents the change in grain-size composition of lignite under cyclic freezing-thawing (FTC) and wetting-drying (WDC). The article shows that in the spring and autumn periods the lignites can be subjected to repeated freezing-thawing and wetting-drying, which determines the possibility of changing their grain-size composition and structure. Experimental studies in laboratory conditions on the influence of cyclic freezing-thawing (FTC) and wetting-drying (WDC) on the quality indicators of lignites have been carried out, their granulometric (fractional) composition has been studied. Freezing-thawing cycle conditions are as follows (FTC): minimum exposure temperature: -20°C;maximum: +5°C;relative humidity: 30%;number of processing cycles: 3. Wetting-drying cycles are as follows (WDC): drying temperatures are +20, +40, +60, +80°C, drying time 90 minutes, the coals are further subjected to rain (soaking) for a period of water saturation to humidity of 30% - 40% and dry again. The number of wetting-drying cycles is 3 times. The tests have revealed the destructive effects of FTC and WDC on the samples of lower metamorphic grade coal, and the cycles of wet-dry lead to the much higher yield of fine sizes (-6+0;-13+0 mm) than the cycles of freeze-thaw. Furthermore, it is found that the increase in the yield of fines depends on the heating temperature: coal disintegration proceeds more intensively at a higher temperature of drying.展开更多
The resistance torque of a piston stage II com- pressor generates strenuous fluctuations in a rotational period, and this can lead to negative influences on the working performance of the compressor. To restrain the s...The resistance torque of a piston stage II com- pressor generates strenuous fluctuations in a rotational period, and this can lead to negative influences on the working performance of the compressor. To restrain the strenuous fluctuations in the piston stage II compressor, a variable duty-cycle control method based on the resistance torque is proposed. A dynamic model of a stage II com- pressor is set up, and the resistance torque and other characteristic parameters are acquired as the control tar- gets. Then, a variable duty-cycle control method is applied to track the resistance torque, thereby improving the working performance of the compressor. Simulated results show that the compressor, driven by the proposed method, requires lower current, while the rotating speed and the output torque remain comparable to the traditional vari- able-frequency control methods. A variable duty-cycle control system is developed, and the experimental results prove that the proposed method can help reduce the specific power, input power, and working noise of the compressor to 0.97 kW.m-3.min-1, 0.09 kW and 3.10 dB, respectively, under the same conditions of discharge pressure of 2.00 MPa and a discharge volume of 0.095 m3/rain. The proposed variable duty-cycle control method tracks the resistance torque dynamically, and improves the working performance of a Stage II Compressor. The pro- posed variable duty-cycle control method can be applied to other compressors, and can provide theoretical guidance for the compressor.展开更多
Using a new low-temperature dynamic triaxial apparatus, the influence law of freezing-thawing cycles on clay shear strength is studied. In this research, the concept of correction coefficients of freezing-thawing cycl...Using a new low-temperature dynamic triaxial apparatus, the influence law of freezing-thawing cycles on clay shear strength is studied. In this research, the concept of correction coefficients of freezing-thawing cycles on clay static strength, cohesion and internal friction angles is proposed, and the change patterns, correction curves and regressive formulae of clay static strength, cohesion and internal friction angles under freezing-thawing cycles are given. The test results indicate that with increasing numbers of freezing-thawing cycles, the clay static strength and cohesion decrease exponentially but the internal friction angle increases exponentially. The performance of static strength, cohesion and internal friction angles are different with increasing numbers of freezing-thawing cycles, i.e., the static strength decreases constantly until about 30% of the initial static strength prior to the freezing-thawing cycling and then stays basically stable. After 5-7 freezing-thawing cycles, the cohesion decreases gradually to about 70% of the initial cohesion. The internal friction angle increases about 20% after the first freezing-thawing cycle, then increases gradually close to a stable value which is an increase of about 40% of the internal friction angle. The freezing-thawing process can increase the variation of the density of the soil samples; therefore, strict density discreteness standards of frozen soil sample preparation should be established to ensure the reliability of the test results.展开更多
The characteristics of reactive magnesia(MgO)-carbonated silt in respect to long-term stability have not been well understood in severely cold climate despite the usage of reactive MgO in enhancing the engineering per...The characteristics of reactive magnesia(MgO)-carbonated silt in respect to long-term stability have not been well understood in severely cold climate despite the usage of reactive MgO in enhancing the engineering performances.Under the binder content of 15%and initial water content of 25%,MgO-admixed silt specimens were carbonized for 3 h and 6 h and then subjected to different numbers of freezingthawing(F-T)cycles.After different F-T cycles,the physico-mechanical properties of MgO-carbonated silt were analyzed in comparison with Portland cement(PC)-stabilized silt through physical and unconfined compression tests.Besides,a series of micro tests on MgO-carbonated specimens was performed including X-ray diffraction(XRD),scanning electron microscopy(SEM)and mercury intrusion porosimetry(MIP)tests.The results demonstrate that both mass change ratio and moisture content of carbonated/stabilized silt decrease,and these values of MgO-carbonated silt are significantly lower while the density is higher compared to PC-stabilized silt.The strengths and moduli of MgO-carbonated silt are still two times higher than those of PC-stabilized specimens and the strength change ratio of keeps above0.8 after F-T cycles.There is no visible transformation between nesquehonite and dypingite/hydromagnesite,although the XRD peaks of nesquehonite decrease and the bonding and filling effects weaken slightly.After 6 and 10 F-T cycles,the pore-size characteristics changed from a unimodal distribution to a three-peak and bimodal distribution,respectively.The total,macro and large pore volumes increase obviously while the medium and small pore volumes decrease except for intra-aggregate pore.The findings show better F-T durability of MgO-carbonated silt,which would be helpful for facilitating the application of MgO carbonation in the soil treatment.展开更多
Background:The cell cycle is at the center of cellular activities and is orchestrated by complex regulatory mechanisms,among which transcriptional regulation is one of the most important components.Alternative splicin...Background:The cell cycle is at the center of cellular activities and is orchestrated by complex regulatory mechanisms,among which transcriptional regulation is one of the most important components.Alternative splicing dramatically expands the regulatory network by producing transcript isoforms of genes to exquisitely control the cell cycle.However,the patterns of transcript isoform expression in the cell cycle are unclear.Therapies targeting cell cycle checkpoints are commonly used as anticancer therapies,but none of them have been designed or evaluated at the alternative splicing transcript level.The utility of these transcripts as markers of cell cycle-related drug sensitivity is still unknown,and studies on the expression patterns of cell cycle-targeting drug-related transcripts are also rare.Methods:To explore alternative splicing patterns during cell cycle progression,we performed sequential transcriptomic assays following cell cycle synchronization in colon cancer HCT116 and breast cancer MDA-MB-231 cell lines,using flow cytometry and reference cell cycle transcripts to confirm the cell cycle phases of samples,and we developed a new algorithm to describe the periodic patterns of transcripts fluctuating during the cell cycle.Genomics of Drug Sensitivity in Cancer(GDSC)drug sensitivity datasets and Cancer Cell Line Encyclopedia(CCLE)transcript datasets were used to assess the correlation of genes and their transcript isoforms with drug sensitivity.We identified transcripts associated with typical drugs targeting cell cycle by determining correlation coefficients.Cytotoxicity assays were used to confirm the effect of ENST00000257904 against cyclin dependent kinase 4/6(CDK4/6)inhibitors.Finally,alternative splicing transcripts associated with mitotic(M)phase arrest were analyzed using an RNA synthesis inhibition assay and transcriptome analysis.Results:We established high-resolution transcriptome datasets of synchronized cell cycle samples from colon cancer HCT116 and breast cancer MDA-MB-231 cells.The results of the cell cycle assessment showed that 43,326,41,578 and 29,244 transcripts were found to be periodically expressed in HeLa,HCT116 and MDA-MB-231 cells,respectively,among which 1280 transcripts showed this expression pattern in all three cancer cell lines.Drug sensitivity assessments showed that a large number of these transcripts displayed a higher correlation with drug sensitivity than their corresponding genes.Cell cycle-related drug screening showed that the level of the CDK4 transcript ENST00000547281 was more significantly associated with the resistance of cells to CDK4/6 inhibitors than the level of the CDK4 reference transcript ENST00000257904.The transcriptional inhibition assay following M phase arrest further confirmed the M-phase-specific expression of the splicing transcripts.Combined with the cell cycle-related drug screening,the results also showed that a set of periodic transcripts,for example,ENST00000314392(a dolichylphosphate mannosyltransferase polypeptide 2 isoform transcript),was more associated with drug sensitivity than the levels of their corresponding gene transcripts.Conclusions:In summary,we identified a panel of cell cycle-related periodic transcripts and found that the levels of transcripts of drug target genes showed different values for predicting drug sensitivity,providing novel insights into alternative splicing-related drug development and evaluation.展开更多
Intra-tumor heterogeneity is now arguably one of the most-studied topics in tumor biology,as it represents a major obstacle to effective cancer treatment.Since tumor cells are highly diverse at genetic,epigenetic,and ...Intra-tumor heterogeneity is now arguably one of the most-studied topics in tumor biology,as it represents a major obstacle to effective cancer treatment.Since tumor cells are highly diverse at genetic,epigenetic,and phenotypic levels,intra-tumor heterogeneity can be assumed as an important contributing factor to the nullification of chemotherapeutic effects,and recurrence of the tumor.Based on the role of heterogeneous subpopulations of cancer cells with varying cell-cycle dynamics and behavior during cancer progression and treatment;herein,we aim to establish a comprehensive definition for adaptation of neoplastic cells against therapy.We discuss two parallel and yet distinct subpopulations of tumor cells that play pivotal roles in reducing the effects of chemotherapy:"resistant"and"tolerant"popula-tions.Furthermore,this review also highlights the impact of the quiescent phase of the cell cycle as a survival mechanism for cancer cells.Beyond understanding the mechanisms under-lying the quiescence,it provides an insightful perspective on cancer stem cells(CsCs)and their dual and intertwined functions based on their cell cycle state in response to treatment.More-over,CSCs,epithelial-mesenchymal transformed cells,circulating tumor cells(CTCs),and disseminated tumor cells(DTCs),which are mostly in a quiescent state of the cell cycle are proved to have multiple biological links and can be implicated in our viewpoint of cell cycle heterogeneity in tumors.Overall,increasing our knowledge of cell cycle heterogeneity is a key to identifying new therapeutic solutions,and this emerging concept may provide us with new opportunities to prevent the dreadful cancer recurrence.展开更多
Summary: The purpose of this study was to investigate the molecular mechanism by which miR-21 and its target genes mediate radiation resistance of glioblastoma cells. Real-time PCR was employed to detect miR-21 expre...Summary: The purpose of this study was to investigate the molecular mechanism by which miR-21 and its target genes mediate radiation resistance of glioblastoma cells. Real-time PCR was employed to detect miR-21 expression in normal brain tissues, glioblastoma tissues and glioblastoma cell lines (A172, T98G and U87MG). T98G cells were transfected with anti-miR-21 oligonucleotides, or plasmids con- taining PDCD4 or hMSH2 (PDCD4-pcDNA3 and hMSH2-pcDNA3). The survival curve was obtained to investigate the sensitivity of T98G cells to radiation. Cell apoptosis was measured by using the Cas- pase-3/7 kit and cell cycle by flow cytometry. Western blotting was performed to detect the expression of hMSH2 and PDCD4 in miR-21-inhibiting T98G cells. The results showed that miR-21 expression in glioblastoma cells and tissues was conversely associated with the radiation sensitivity. Over-expression of miR-21 resulted in radiation resistance, while knockdown of miR-21 led to higher sensitivity of glioblastma cells to radiation. After miR-21 knockdown, the apoptosis of T98G cells was significantly increased and the G2 phase arrest was more significant. In addition, miR-21 knockdown increased the expression of endogenous PDCD4 and hMSH2, which contributed to the apoptosis and G2 arrest of T98G cells. The findings suggested that miR-21 may mediate the resistance of glioblastoma cells against radiation via its target genes PDCD4 and hMSH2. MiR-21 and its target genes may be used as potential molecular targets for clinical radiotherapy sensitization in the future.展开更多
It has been widely recognized that loess has a low stability and permeability,and it is susceptible to a sudden decrease in total volume or collapse upon wetting.When the railway subgrade was under the dynamic trainlo...It has been widely recognized that loess has a low stability and permeability,and it is susceptible to a sudden decrease in total volume or collapse upon wetting.When the railway subgrade was under the dynamic trainload,the loess subgrade was prone to instability and liquefaction.loess is higher than that of the cement modified loess,but lower than that of the MPG modified loess.However,the coefficient of permeability for the MPGcement modified loess has an opposite result,and the MPG-cement modified loess specimens have the best frost resistance.In addition,the mechanism of MPG-Bao Zhong railway is a key railway for Guyuan city,in Ningxia province of China,which is an important city of the Belt and Road.Due to the influence of largearea flood irrigation on the farmland,the subgrade had a degree of settlement.The settlement had not been alleviated after three treatments,which seriously affected the safety of the train.For this reason,cement,Modified Phospho Gypsum(MPG)and MPGcement were used to reinforce the subgrade loess,and the unconfined compressive strength test,permeability test and freeze-thaw cycle test were carried out.Then the compressive strength,impermeability and frost resistance of the three were analyzed and compared.The results indicate that the compressive strength of the MPG-cement modified cement modified loess is discussed.It is found that cement and MPG have two hydration reactions with water in loess.Ettringite,the hydration reaction product,which not only fills the pores,restricts the movement of the soil particles,but also acts as a connecting soil particle in the soil particles.Therefore,the strength of the modified loess continues to increase,and the physical properties of the modified loess are improved.展开更多
AIM: To investigate the expression of miR-210 and the role it plays in the cell cycle to regulate radioresistance in oesophageal squamous cell carcinoma(ESCC). METHODS: Mi R-210 expression was evaluated in 37 pairs of...AIM: To investigate the expression of miR-210 and the role it plays in the cell cycle to regulate radioresistance in oesophageal squamous cell carcinoma(ESCC). METHODS: Mi R-210 expression was evaluated in 37 pairs of ESCC tissues and matched para-tumorous normal oesophageal tissues from surgical patients who had not received neoadjuvant therapy, and in the cells of two novel radioresistant cell lines, TE-1R and Eca-109 R, using quantitative reverse transcription-polymerase chain reaction(q RT-PCR). The transient up-regulation of mi R-210 expression in TE-1R and Eca-109 R cells was studied using liposomes and was confirmed using qR T-PCR. The rate of cell survival after a series of radio-treatment doses was evaluated using the cloneformation assay. Flow cytometry was used to detect the changes to the cell cycle patterns due to radiation treatment. RT-PCR and Western blot were used to detect the expression of ataxia telangiectasia mutated(ATM) and DNA dependent protein kinase(DNA-PKcs) after irradiation, and the cell sphere formation assay was used to evaluate the proliferative ability of the cancer stem-like cells.RESULTS: The level of mi R-210 expression was significantly decreased, by 21.3% to 97.2%, with the average being 39.2% ± 16.1%, in the ESCC tissues of most patients(81.1%, 30 of 37 vs patients with high mi R-210 expression, P < 0.05). A low level of expression of miR-210 was correlated with a poorly differentiated pathological type(P < 0.01) but was not correlated with the T-stage or lymph node infiltration(both P > 0.05). Early local recurrences(< 18 mo, n = 19) after radiotherapy were significantly related with low miR-210 expression(n = 13, P < 0.05). The level of mi R-210 was decreased by approximately 73%(vs TE-1, 0.27 ± 0.10, P < 0.01) in the established radioresistant TE-IR cell line and by 52%(vs Eca-109, 0.48 ± 0.17, P < 0.05) in the corresponding Eca-109 R line. Transient transfection with a mi R-210 precursor increased the level of mi R-210 expression, leading to a significant increase in cell survival after radiotherapy(P < 0.05). Twenty-four hours after radiation, the proportion of pmiR-210 cells in S phase was increased(vs control cells, 30.4% ± 0.4%, and vs untreated TE-1R cells, 23.3% ± 0.7%, P < 0.05 for both). The levels of DNA-PKcs(0.21 ± 0.07) and ATM(0.12 ± 0.03, P < 0.05) proteins were significantly lower in the PmiR-210 cells than in control cells, but no differences were found in the levels of the corresponding mR NAs in the two cell types(P > 0.05 for all). Exogenous mi R-210 expression decreased the diameter of pmi R-210 cell spheres(vs control cells, 0.60 ± 0.14, P < 0.05).CONCLUSION: Mi R-210 expression is negatively correlated with the pathological type and the local survivalrate after radiotherapy, and high expression of miR-210 may reverse the radioresistance of ESCC stem-like cells.展开更多
large diameter internal thread of high-strength steel(LDITHSS) manufactured by traditional methods always has the problems of low accuracy and short life. Compared with traditional methods, the cold extrusion proces...large diameter internal thread of high-strength steel(LDITHSS) manufactured by traditional methods always has the problems of low accuracy and short life. Compared with traditional methods, the cold extrusion process is an effective means to realize higher accuracy and longer life. The low-cycle fatigue properties of LDITHSS are obtained by experiments, and the initiation and propagation of fatigue cracks are observed by scanning electron microscope(SEM). Based on the mechanical properties, surface microstructure and residual stress, the strengthening mechanism of cold extruded large diameter internal thread(LDIT) is discussed. The results show that new grains or sub-grains can be formed on the surface of LDIT due to grain segmentation and grain refinement during cold extrusion. The fibrous structures appear as elongated and streamlined along the normal direction of the tooth surface which leads to residual compressive stress on the extruded surface. The maximum tension stress of LDIT after cold extrusion is found to be 192.55 k N. Under low stress cycling, the yield stress on thread increases, the propagation rate of crack reduces, the fatigue life is thus improved significantly with decreasing surface grain diameter and the average fatigue life increases to 45.539×10~3 cycle when the maximum applied load decreases to 120 k N. The low cycle fatigue and strengthening mechanism of cold extruded LDIT revealed by this research has significant importance to promote application of internal thread by cold extrusion processing.展开更多
In coastal Antarctica, frequent freezing-thawing cycles (FTCs) and changes to the hydrological conditions may affect methane (CH4) and nitrous oxide (N2O) production and respiration rates in tundra soils, which ...In coastal Antarctica, frequent freezing-thawing cycles (FTCs) and changes to the hydrological conditions may affect methane (CH4) and nitrous oxide (N2O) production and respiration rates in tundra soils, which are difficult to observe in situ. Tundra soils including omithogenic tundra soil (OAS), seal colony soil (SCS) and emperor penguin colony soil (EPS) were collected. In laboratory, we investigated the effects of FTCs and water addition on potential N2O and CH4 production and respiration rates in the soils. The CH4 fluxes from OAS and SCS were much less than that from EPS. Meanwhile, the N2O fluxes from OAS and EPS were much less than that from SCS. The N2O production rates from all soils were extremely low during freezing, but rapidly increased following thawing. In all cases, FTC also induced considerably enhanced soil respiration, indicating that soil respiration response was sensitive to the FTCs. The highest cumulative rates of CH4, N2O and CO2 were 59.5 mg CH4-C·kg-1 in EPS, 6268.8μg N2O-N·kg-1 in SCS and 3522.1mg CO2-C·kg-1 in OAS. Soil water addition had no significant effects on CH4 production and respiration rates, but it could reduce N2O production in OAS and EPS, and it stimulated N2O production in SCS. Overall, CH4 and N2O production rates showed a trade-off relationship during the three FTCs. Our results indicated that FTCs greatly stimulated soil N2O and CO2 production, and water increase has an important effect on soil N2O production in coastal Antarctic tundra.展开更多
The frost resistance and compressive strength degradation of concrete under the simultaneous action of compressive load and freeze-thaw cycles were experimentally investigated. Air-entrained and non-air-entrained spec...The frost resistance and compressive strength degradation of concrete under the simultaneous action of compressive load and freeze-thaw cycles were experimentally investigated. Air-entrained and non-air-entrained specimens with different water/cement(w/c) ratios were subjected to different compressive stress by specially designed apparatus, while the specimens suffered freeze-thaw cycles. In order to track the strength degradation process, the nondestructive tests were carried out after each freeze-thaw cycle got the residual strength for each specimen. Based on the experimental data, a variable Kss was proposed to describe the damage velocity. Experimental results indicate that the deterioration processes are accelerated by the compressive loads, and the damage velocity increases with the increases of the preloading levels and w/c ratios. The air entrainment decreases the damage velocity and improves the frost resistance of non-air-entrained concrete, although it would reduce the compressive strength of concrete.展开更多
Use of stainless reinforcing steel (SRS) in reinforced concrete (RC) structures is a promising solution to corrosion issues. However, for SRS to be used in seismic applications, several mechanical properties need ...Use of stainless reinforcing steel (SRS) in reinforced concrete (RC) structures is a promising solution to corrosion issues. However, for SRS to be used in seismic applications, several mechanical properties need to be investigated. These include specified and actual yield strengths, tensile strengths, uniform elongations and low-cycle fatigue behavior. Three types of SRSs (Talley S24100, Talley 316LN and Talley 2205) were tested and the results are reported in this paper. They were compared with the properties of A706 carbon reinforcing steel (RS), which is typical for seismic applications, and MMFX II, which is a high strength, corrosion resistant RS. Low-cycle fatigue tests of the RS coupons were conducted under strain control with constant amplitude to obtain strain life models of the steels. Test results show that the SRSs have slightly lower moduli of elasticity, higher uniform elongations before necking, and better low-cycle fatigue performance than A706 and MMFX II. All five types of RSs tested satisfy the requirements of the ACI 318 code on the lower limit of the tensile to yield strength ratio. Except Talley 2205, the other four types of RSs investigated meet the ACI 318 requirement that the actual yield strength does not exceed the specified yield strength by more than 18 ksi (124 MPa). Among the three types of SRSs tested, Talley S24100 possesses the highest uniform elongation before necking, and the best low-cycle fatigue performance.展开更多
Objective:To study the relationship between miR-100 expression in cervical cancer tissue and cisplatin resistance.Methods: A total of 107 cases of cervical cancer tissues from those who received cisplatin chemotherapy...Objective:To study the relationship between miR-100 expression in cervical cancer tissue and cisplatin resistance.Methods: A total of 107 cases of cervical cancer tissues from those who received cisplatin chemotherapy in Huanggan Central Hospital between May 2013 and October 2016 were collected as the clinical samples and divided into chemotherapy-responsive cisplatin-sensitive cervical cancer tissue and chemotherapy-irresponsive cisplatin-sensitive cervical cancer tissue according to the curative effect of chemotherapy. The miR-100 expression as well as the expression of drug resistance-related genes, cell cycle-related genes and cell invasion-related genes was determined.Results: The miR-100 expression in cisplatin-resistant cervical cancer tissue was significantly lower than that in cisplatin-sensitive cervical cancer tissue while Nek2, P-gp, GST-π, Topo-II, SP2, CyclinD1, CyclinG1, CDK4, CDK5, MMP1, PAR1, RbAp48, Vimentin and N-cadherin expression were significantly higher than those in cisplatin-sensitive cervical cancer tissue;the miR-100 expression was negatively correlated with Nek2, P-gp, GST-π, Topo-II, SP2, CyclinD1, CyclinG1, CDK4, CDK5, MMP1, PAR1, RbAp48, Vimentin and N-cadherin expression.Conclusion: The lower expression of miR-100 in cervical cancer tissue is closely associated with cisplatin resistance.展开更多
In the performance experiment of organic Rankine cycle power generation experimental system, the loadresistance-regulation method is one of the most important regulation methods. However, the regulation law has not be...In the performance experiment of organic Rankine cycle power generation experimental system, the loadresistance-regulation method is one of the most important regulation methods. However, the regulation law has not been clear enough to guide the experiment, which is unfavorable to the experimental research on organic Rankine cycle. In this paper the regulation law of turbine and generator by the load-resistance-regulation method is studied theoretically and experimentally. The results show that when the thermal cycle parameters keep constant, the turbine speed increases with the increase of load resistance and there is a maximum value of transmission-generator efficiency with the variation of the turbine speed; when the turbine speed and generator speed keep constant, the transmissiongenerator efficiency decreases and gradually tends to zero with the increase of load resistance.展开更多
The aims of this study are to determine the population genetic structure of Rhizoctonia solani,associated with potato,and to assess its resistance degree to pencycuron and thiabendazole fungicides.A total of 57 strain...The aims of this study are to determine the population genetic structure of Rhizoctonia solani,associated with potato,and to assess its resistance degree to pencycuron and thiabendazole fungicides.A total of 57 strains of R.Solani were isolated from different potato crop fields in Mexico,and were classified according to their anastomosis group(AG)using the polymerase chain reaction(PCR)and restriction fragment length polymorphism(RFLP)-based analysis.Then,the amplified fragments were digested with four different endonucleases(Mse I,Ava II,Mun I and Hinc II).The Repetitive Element Sequence-Based PCR(rep-PCR)technique was used to determine the genetic diversity in R.solani populations.Results obtained by PCR-RFLP showed that 81%of the isolates were identified as belonging to AG-3 group,14%to AG1-1B and 5%to AG-11 group.In response to fungicides inhibition,IC_(50)between 0.014-0.039 mg a.i./L for pencycuron,and 0.82 to 2.91 for thiabendazole were determined,This IC_(50)value showed that the resistance factor(RF)values ranged from 1.4 to 3.945 and 0.27 to 0.97,respectively;this tendency suggests that isolates are susceptible to thiabendazole.The AG groups showed a heterogeneous resistance to pencycuron and thiabendazole,being more tolerant to these fungicides AG1-1B and AG-11 groups.The genetic analysis shows a low genetic diversity among(P-value 0.3225)and within(P-value 0.3275)populations;this can indicate a clonal reproduction and little parasexual cycle among the analyzed isolations.展开更多
文摘The paper presents the change in grain-size composition of lignite under cyclic freezing-thawing (FTC) and wetting-drying (WDC). The article shows that in the spring and autumn periods the lignites can be subjected to repeated freezing-thawing and wetting-drying, which determines the possibility of changing their grain-size composition and structure. Experimental studies in laboratory conditions on the influence of cyclic freezing-thawing (FTC) and wetting-drying (WDC) on the quality indicators of lignites have been carried out, their granulometric (fractional) composition has been studied. Freezing-thawing cycle conditions are as follows (FTC): minimum exposure temperature: -20°C;maximum: +5°C;relative humidity: 30%;number of processing cycles: 3. Wetting-drying cycles are as follows (WDC): drying temperatures are +20, +40, +60, +80°C, drying time 90 minutes, the coals are further subjected to rain (soaking) for a period of water saturation to humidity of 30% - 40% and dry again. The number of wetting-drying cycles is 3 times. The tests have revealed the destructive effects of FTC and WDC on the samples of lower metamorphic grade coal, and the cycles of wet-dry lead to the much higher yield of fine sizes (-6+0;-13+0 mm) than the cycles of freeze-thaw. Furthermore, it is found that the increase in the yield of fines depends on the heating temperature: coal disintegration proceeds more intensively at a higher temperature of drying.
基金Supported by National Natural Science Foundation of China(Grant No.51275452)Zhejiang Provincical Natural Science Foundation of China(Grant No.LY14E050021)Commonweal Technology Project of Science and Technology Department of Zhejiang Province,China(Grant No.2015C31071)
文摘The resistance torque of a piston stage II com- pressor generates strenuous fluctuations in a rotational period, and this can lead to negative influences on the working performance of the compressor. To restrain the strenuous fluctuations in the piston stage II compressor, a variable duty-cycle control method based on the resistance torque is proposed. A dynamic model of a stage II com- pressor is set up, and the resistance torque and other characteristic parameters are acquired as the control tar- gets. Then, a variable duty-cycle control method is applied to track the resistance torque, thereby improving the working performance of the compressor. Simulated results show that the compressor, driven by the proposed method, requires lower current, while the rotating speed and the output torque remain comparable to the traditional vari- able-frequency control methods. A variable duty-cycle control system is developed, and the experimental results prove that the proposed method can help reduce the specific power, input power, and working noise of the compressor to 0.97 kW.m-3.min-1, 0.09 kW and 3.10 dB, respectively, under the same conditions of discharge pressure of 2.00 MPa and a discharge volume of 0.095 m3/rain. The proposed variable duty-cycle control method tracks the resistance torque dynamically, and improves the working performance of a Stage II Compressor. The pro- posed variable duty-cycle control method can be applied to other compressors, and can provide theoretical guidance for the compressor.
基金Scientific Research Fund of Institute of Engineering Mechanics,China Earthquake Administration under Grant No.2018D12National Natural Science Foundation of Heilongjiang Province under Grant No.E 2016045+1 种基金National Natural Science Foundation of China under Grant No.5137816451508140
文摘Using a new low-temperature dynamic triaxial apparatus, the influence law of freezing-thawing cycles on clay shear strength is studied. In this research, the concept of correction coefficients of freezing-thawing cycles on clay static strength, cohesion and internal friction angles is proposed, and the change patterns, correction curves and regressive formulae of clay static strength, cohesion and internal friction angles under freezing-thawing cycles are given. The test results indicate that with increasing numbers of freezing-thawing cycles, the clay static strength and cohesion decrease exponentially but the internal friction angle increases exponentially. The performance of static strength, cohesion and internal friction angles are different with increasing numbers of freezing-thawing cycles, i.e., the static strength decreases constantly until about 30% of the initial static strength prior to the freezing-thawing cycling and then stays basically stable. After 5-7 freezing-thawing cycles, the cohesion decreases gradually to about 70% of the initial cohesion. The internal friction angle increases about 20% after the first freezing-thawing cycle, then increases gradually close to a stable value which is an increase of about 40% of the internal friction angle. The freezing-thawing process can increase the variation of the density of the soil samples; therefore, strict density discreteness standards of frozen soil sample preparation should be established to ensure the reliability of the test results.
基金the support of the National Natural Science Foundation of China(Grant Nos.41902286 and 41972269)Open Research Fund of State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences(Grant No.Z019026)。
文摘The characteristics of reactive magnesia(MgO)-carbonated silt in respect to long-term stability have not been well understood in severely cold climate despite the usage of reactive MgO in enhancing the engineering performances.Under the binder content of 15%and initial water content of 25%,MgO-admixed silt specimens were carbonized for 3 h and 6 h and then subjected to different numbers of freezingthawing(F-T)cycles.After different F-T cycles,the physico-mechanical properties of MgO-carbonated silt were analyzed in comparison with Portland cement(PC)-stabilized silt through physical and unconfined compression tests.Besides,a series of micro tests on MgO-carbonated specimens was performed including X-ray diffraction(XRD),scanning electron microscopy(SEM)and mercury intrusion porosimetry(MIP)tests.The results demonstrate that both mass change ratio and moisture content of carbonated/stabilized silt decrease,and these values of MgO-carbonated silt are significantly lower while the density is higher compared to PC-stabilized silt.The strengths and moduli of MgO-carbonated silt are still two times higher than those of PC-stabilized specimens and the strength change ratio of keeps above0.8 after F-T cycles.There is no visible transformation between nesquehonite and dypingite/hydromagnesite,although the XRD peaks of nesquehonite decrease and the bonding and filling effects weaken slightly.After 6 and 10 F-T cycles,the pore-size characteristics changed from a unimodal distribution to a three-peak and bimodal distribution,respectively.The total,macro and large pore volumes increase obviously while the medium and small pore volumes decrease except for intra-aggregate pore.The findings show better F-T durability of MgO-carbonated silt,which would be helpful for facilitating the application of MgO carbonation in the soil treatment.
基金supported by grants from the National Key Research and Development Program of China(2021YFF1201300)the National Natural Science Foundation of China(81872280,82073094)+2 种基金the CAMS Innovation Fund for Medical Sciences(CIFMS)(2021-I2M-1-014)the Open Issue of State Key Laboratory of Molecular Oncology(SKL-KF-2021-16)the Independent Issue of State Key Laboratory of Molecular Oncology(SKL-2021-16).
文摘Background:The cell cycle is at the center of cellular activities and is orchestrated by complex regulatory mechanisms,among which transcriptional regulation is one of the most important components.Alternative splicing dramatically expands the regulatory network by producing transcript isoforms of genes to exquisitely control the cell cycle.However,the patterns of transcript isoform expression in the cell cycle are unclear.Therapies targeting cell cycle checkpoints are commonly used as anticancer therapies,but none of them have been designed or evaluated at the alternative splicing transcript level.The utility of these transcripts as markers of cell cycle-related drug sensitivity is still unknown,and studies on the expression patterns of cell cycle-targeting drug-related transcripts are also rare.Methods:To explore alternative splicing patterns during cell cycle progression,we performed sequential transcriptomic assays following cell cycle synchronization in colon cancer HCT116 and breast cancer MDA-MB-231 cell lines,using flow cytometry and reference cell cycle transcripts to confirm the cell cycle phases of samples,and we developed a new algorithm to describe the periodic patterns of transcripts fluctuating during the cell cycle.Genomics of Drug Sensitivity in Cancer(GDSC)drug sensitivity datasets and Cancer Cell Line Encyclopedia(CCLE)transcript datasets were used to assess the correlation of genes and their transcript isoforms with drug sensitivity.We identified transcripts associated with typical drugs targeting cell cycle by determining correlation coefficients.Cytotoxicity assays were used to confirm the effect of ENST00000257904 against cyclin dependent kinase 4/6(CDK4/6)inhibitors.Finally,alternative splicing transcripts associated with mitotic(M)phase arrest were analyzed using an RNA synthesis inhibition assay and transcriptome analysis.Results:We established high-resolution transcriptome datasets of synchronized cell cycle samples from colon cancer HCT116 and breast cancer MDA-MB-231 cells.The results of the cell cycle assessment showed that 43,326,41,578 and 29,244 transcripts were found to be periodically expressed in HeLa,HCT116 and MDA-MB-231 cells,respectively,among which 1280 transcripts showed this expression pattern in all three cancer cell lines.Drug sensitivity assessments showed that a large number of these transcripts displayed a higher correlation with drug sensitivity than their corresponding genes.Cell cycle-related drug screening showed that the level of the CDK4 transcript ENST00000547281 was more significantly associated with the resistance of cells to CDK4/6 inhibitors than the level of the CDK4 reference transcript ENST00000257904.The transcriptional inhibition assay following M phase arrest further confirmed the M-phase-specific expression of the splicing transcripts.Combined with the cell cycle-related drug screening,the results also showed that a set of periodic transcripts,for example,ENST00000314392(a dolichylphosphate mannosyltransferase polypeptide 2 isoform transcript),was more associated with drug sensitivity than the levels of their corresponding gene transcripts.Conclusions:In summary,we identified a panel of cell cycle-related periodic transcripts and found that the levels of transcripts of drug target genes showed different values for predicting drug sensitivity,providing novel insights into alternative splicing-related drug development and evaluation.
文摘Intra-tumor heterogeneity is now arguably one of the most-studied topics in tumor biology,as it represents a major obstacle to effective cancer treatment.Since tumor cells are highly diverse at genetic,epigenetic,and phenotypic levels,intra-tumor heterogeneity can be assumed as an important contributing factor to the nullification of chemotherapeutic effects,and recurrence of the tumor.Based on the role of heterogeneous subpopulations of cancer cells with varying cell-cycle dynamics and behavior during cancer progression and treatment;herein,we aim to establish a comprehensive definition for adaptation of neoplastic cells against therapy.We discuss two parallel and yet distinct subpopulations of tumor cells that play pivotal roles in reducing the effects of chemotherapy:"resistant"and"tolerant"popula-tions.Furthermore,this review also highlights the impact of the quiescent phase of the cell cycle as a survival mechanism for cancer cells.Beyond understanding the mechanisms under-lying the quiescence,it provides an insightful perspective on cancer stem cells(CsCs)and their dual and intertwined functions based on their cell cycle state in response to treatment.More-over,CSCs,epithelial-mesenchymal transformed cells,circulating tumor cells(CTCs),and disseminated tumor cells(DTCs),which are mostly in a quiescent state of the cell cycle are proved to have multiple biological links and can be implicated in our viewpoint of cell cycle heterogeneity in tumors.Overall,increasing our knowledge of cell cycle heterogeneity is a key to identifying new therapeutic solutions,and this emerging concept may provide us with new opportunities to prevent the dreadful cancer recurrence.
基金supported by grants from the National Natural Science Foundation of China(Nos.81201820,81101691)supported by Specialized Research Fund for the Doctoral Program of Higher Education(No.20100142120041)
文摘Summary: The purpose of this study was to investigate the molecular mechanism by which miR-21 and its target genes mediate radiation resistance of glioblastoma cells. Real-time PCR was employed to detect miR-21 expression in normal brain tissues, glioblastoma tissues and glioblastoma cell lines (A172, T98G and U87MG). T98G cells were transfected with anti-miR-21 oligonucleotides, or plasmids con- taining PDCD4 or hMSH2 (PDCD4-pcDNA3 and hMSH2-pcDNA3). The survival curve was obtained to investigate the sensitivity of T98G cells to radiation. Cell apoptosis was measured by using the Cas- pase-3/7 kit and cell cycle by flow cytometry. Western blotting was performed to detect the expression of hMSH2 and PDCD4 in miR-21-inhibiting T98G cells. The results showed that miR-21 expression in glioblastoma cells and tissues was conversely associated with the radiation sensitivity. Over-expression of miR-21 resulted in radiation resistance, while knockdown of miR-21 led to higher sensitivity of glioblastma cells to radiation. After miR-21 knockdown, the apoptosis of T98G cells was significantly increased and the G2 phase arrest was more significant. In addition, miR-21 knockdown increased the expression of endogenous PDCD4 and hMSH2, which contributed to the apoptosis and G2 arrest of T98G cells. The findings suggested that miR-21 may mediate the resistance of glioblastoma cells against radiation via its target genes PDCD4 and hMSH2. MiR-21 and its target genes may be used as potential molecular targets for clinical radiotherapy sensitization in the future.
文摘It has been widely recognized that loess has a low stability and permeability,and it is susceptible to a sudden decrease in total volume or collapse upon wetting.When the railway subgrade was under the dynamic trainload,the loess subgrade was prone to instability and liquefaction.loess is higher than that of the cement modified loess,but lower than that of the MPG modified loess.However,the coefficient of permeability for the MPGcement modified loess has an opposite result,and the MPG-cement modified loess specimens have the best frost resistance.In addition,the mechanism of MPG-Bao Zhong railway is a key railway for Guyuan city,in Ningxia province of China,which is an important city of the Belt and Road.Due to the influence of largearea flood irrigation on the farmland,the subgrade had a degree of settlement.The settlement had not been alleviated after three treatments,which seriously affected the safety of the train.For this reason,cement,Modified Phospho Gypsum(MPG)and MPGcement were used to reinforce the subgrade loess,and the unconfined compressive strength test,permeability test and freeze-thaw cycle test were carried out.Then the compressive strength,impermeability and frost resistance of the three were analyzed and compared.The results indicate that the compressive strength of the MPG-cement modified cement modified loess is discussed.It is found that cement and MPG have two hydration reactions with water in loess.Ettringite,the hydration reaction product,which not only fills the pores,restricts the movement of the soil particles,but also acts as a connecting soil particle in the soil particles.Therefore,the strength of the modified loess continues to increase,and the physical properties of the modified loess are improved.
基金Supported by National Natural Science Foundation of China,No.30972962
文摘AIM: To investigate the expression of miR-210 and the role it plays in the cell cycle to regulate radioresistance in oesophageal squamous cell carcinoma(ESCC). METHODS: Mi R-210 expression was evaluated in 37 pairs of ESCC tissues and matched para-tumorous normal oesophageal tissues from surgical patients who had not received neoadjuvant therapy, and in the cells of two novel radioresistant cell lines, TE-1R and Eca-109 R, using quantitative reverse transcription-polymerase chain reaction(q RT-PCR). The transient up-regulation of mi R-210 expression in TE-1R and Eca-109 R cells was studied using liposomes and was confirmed using qR T-PCR. The rate of cell survival after a series of radio-treatment doses was evaluated using the cloneformation assay. Flow cytometry was used to detect the changes to the cell cycle patterns due to radiation treatment. RT-PCR and Western blot were used to detect the expression of ataxia telangiectasia mutated(ATM) and DNA dependent protein kinase(DNA-PKcs) after irradiation, and the cell sphere formation assay was used to evaluate the proliferative ability of the cancer stem-like cells.RESULTS: The level of mi R-210 expression was significantly decreased, by 21.3% to 97.2%, with the average being 39.2% ± 16.1%, in the ESCC tissues of most patients(81.1%, 30 of 37 vs patients with high mi R-210 expression, P < 0.05). A low level of expression of miR-210 was correlated with a poorly differentiated pathological type(P < 0.01) but was not correlated with the T-stage or lymph node infiltration(both P > 0.05). Early local recurrences(< 18 mo, n = 19) after radiotherapy were significantly related with low miR-210 expression(n = 13, P < 0.05). The level of mi R-210 was decreased by approximately 73%(vs TE-1, 0.27 ± 0.10, P < 0.01) in the established radioresistant TE-IR cell line and by 52%(vs Eca-109, 0.48 ± 0.17, P < 0.05) in the corresponding Eca-109 R line. Transient transfection with a mi R-210 precursor increased the level of mi R-210 expression, leading to a significant increase in cell survival after radiotherapy(P < 0.05). Twenty-four hours after radiation, the proportion of pmiR-210 cells in S phase was increased(vs control cells, 30.4% ± 0.4%, and vs untreated TE-1R cells, 23.3% ± 0.7%, P < 0.05 for both). The levels of DNA-PKcs(0.21 ± 0.07) and ATM(0.12 ± 0.03, P < 0.05) proteins were significantly lower in the PmiR-210 cells than in control cells, but no differences were found in the levels of the corresponding mR NAs in the two cell types(P > 0.05 for all). Exogenous mi R-210 expression decreased the diameter of pmi R-210 cell spheres(vs control cells, 0.60 ± 0.14, P < 0.05).CONCLUSION: Mi R-210 expression is negatively correlated with the pathological type and the local survivalrate after radiotherapy, and high expression of miR-210 may reverse the radioresistance of ESCC stem-like cells.
基金Supported by National Natural Science Foundation of China(Grant No.51372216)Jiangsu Science and Technology Plan Project of China(Grant No.BE2015113)Natural Science Foundation of the Jiangsu Higher Education Institutions of China(Grant No.BKJB460016)
文摘large diameter internal thread of high-strength steel(LDITHSS) manufactured by traditional methods always has the problems of low accuracy and short life. Compared with traditional methods, the cold extrusion process is an effective means to realize higher accuracy and longer life. The low-cycle fatigue properties of LDITHSS are obtained by experiments, and the initiation and propagation of fatigue cracks are observed by scanning electron microscope(SEM). Based on the mechanical properties, surface microstructure and residual stress, the strengthening mechanism of cold extruded large diameter internal thread(LDIT) is discussed. The results show that new grains or sub-grains can be formed on the surface of LDIT due to grain segmentation and grain refinement during cold extrusion. The fibrous structures appear as elongated and streamlined along the normal direction of the tooth surface which leads to residual compressive stress on the extruded surface. The maximum tension stress of LDIT after cold extrusion is found to be 192.55 k N. Under low stress cycling, the yield stress on thread increases, the propagation rate of crack reduces, the fatigue life is thus improved significantly with decreasing surface grain diameter and the average fatigue life increases to 45.539×10~3 cycle when the maximum applied load decreases to 120 k N. The low cycle fatigue and strengthening mechanism of cold extruded LDIT revealed by this research has significant importance to promote application of internal thread by cold extrusion processing.
基金supported by the National Natural Science Foundation of China (Grant nos.41576181,41601304 and 41176171)
文摘In coastal Antarctica, frequent freezing-thawing cycles (FTCs) and changes to the hydrological conditions may affect methane (CH4) and nitrous oxide (N2O) production and respiration rates in tundra soils, which are difficult to observe in situ. Tundra soils including omithogenic tundra soil (OAS), seal colony soil (SCS) and emperor penguin colony soil (EPS) were collected. In laboratory, we investigated the effects of FTCs and water addition on potential N2O and CH4 production and respiration rates in the soils. The CH4 fluxes from OAS and SCS were much less than that from EPS. Meanwhile, the N2O fluxes from OAS and EPS were much less than that from SCS. The N2O production rates from all soils were extremely low during freezing, but rapidly increased following thawing. In all cases, FTC also induced considerably enhanced soil respiration, indicating that soil respiration response was sensitive to the FTCs. The highest cumulative rates of CH4, N2O and CO2 were 59.5 mg CH4-C·kg-1 in EPS, 6268.8μg N2O-N·kg-1 in SCS and 3522.1mg CO2-C·kg-1 in OAS. Soil water addition had no significant effects on CH4 production and respiration rates, but it could reduce N2O production in OAS and EPS, and it stimulated N2O production in SCS. Overall, CH4 and N2O production rates showed a trade-off relationship during the three FTCs. Our results indicated that FTCs greatly stimulated soil N2O and CO2 production, and water increase has an important effect on soil N2O production in coastal Antarctic tundra.
基金National Natural Science Foundation of China ( No. 50678101)
文摘The frost resistance and compressive strength degradation of concrete under the simultaneous action of compressive load and freeze-thaw cycles were experimentally investigated. Air-entrained and non-air-entrained specimens with different water/cement(w/c) ratios were subjected to different compressive stress by specially designed apparatus, while the specimens suffered freeze-thaw cycles. In order to track the strength degradation process, the nondestructive tests were carried out after each freeze-thaw cycle got the residual strength for each specimen. Based on the experimental data, a variable Kss was proposed to describe the damage velocity. Experimental results indicate that the deterioration processes are accelerated by the compressive loads, and the damage velocity increases with the increases of the preloading levels and w/c ratios. The air entrainment decreases the damage velocity and improves the frost resistance of non-air-entrained concrete, although it would reduce the compressive strength of concrete.
基金Federal Highway Administration Under Contract No.DTFH61-07-R-00121International Molybdenum Association,Nickel Institute,Talley Metals-A Carpenter Company,North American Stainless and Salit Specialty Steel Through MCEER,University at Buffalo
文摘Use of stainless reinforcing steel (SRS) in reinforced concrete (RC) structures is a promising solution to corrosion issues. However, for SRS to be used in seismic applications, several mechanical properties need to be investigated. These include specified and actual yield strengths, tensile strengths, uniform elongations and low-cycle fatigue behavior. Three types of SRSs (Talley S24100, Talley 316LN and Talley 2205) were tested and the results are reported in this paper. They were compared with the properties of A706 carbon reinforcing steel (RS), which is typical for seismic applications, and MMFX II, which is a high strength, corrosion resistant RS. Low-cycle fatigue tests of the RS coupons were conducted under strain control with constant amplitude to obtain strain life models of the steels. Test results show that the SRSs have slightly lower moduli of elasticity, higher uniform elongations before necking, and better low-cycle fatigue performance than A706 and MMFX II. All five types of RSs tested satisfy the requirements of the ACI 318 code on the lower limit of the tensile to yield strength ratio. Except Talley 2205, the other four types of RSs investigated meet the ACI 318 requirement that the actual yield strength does not exceed the specified yield strength by more than 18 ksi (124 MPa). Among the three types of SRSs tested, Talley S24100 possesses the highest uniform elongation before necking, and the best low-cycle fatigue performance.
文摘Objective:To study the relationship between miR-100 expression in cervical cancer tissue and cisplatin resistance.Methods: A total of 107 cases of cervical cancer tissues from those who received cisplatin chemotherapy in Huanggan Central Hospital between May 2013 and October 2016 were collected as the clinical samples and divided into chemotherapy-responsive cisplatin-sensitive cervical cancer tissue and chemotherapy-irresponsive cisplatin-sensitive cervical cancer tissue according to the curative effect of chemotherapy. The miR-100 expression as well as the expression of drug resistance-related genes, cell cycle-related genes and cell invasion-related genes was determined.Results: The miR-100 expression in cisplatin-resistant cervical cancer tissue was significantly lower than that in cisplatin-sensitive cervical cancer tissue while Nek2, P-gp, GST-π, Topo-II, SP2, CyclinD1, CyclinG1, CDK4, CDK5, MMP1, PAR1, RbAp48, Vimentin and N-cadherin expression were significantly higher than those in cisplatin-sensitive cervical cancer tissue;the miR-100 expression was negatively correlated with Nek2, P-gp, GST-π, Topo-II, SP2, CyclinD1, CyclinG1, CDK4, CDK5, MMP1, PAR1, RbAp48, Vimentin and N-cadherin expression.Conclusion: The lower expression of miR-100 in cervical cancer tissue is closely associated with cisplatin resistance.
基金Supported by the National Natural Science Foundation of China(No.51306198)the Specialized Research Fund for the Doctoral Program of Higher Education of China(No.20110032110046)
文摘In the performance experiment of organic Rankine cycle power generation experimental system, the loadresistance-regulation method is one of the most important regulation methods. However, the regulation law has not been clear enough to guide the experiment, which is unfavorable to the experimental research on organic Rankine cycle. In this paper the regulation law of turbine and generator by the load-resistance-regulation method is studied theoretically and experimentally. The results show that when the thermal cycle parameters keep constant, the turbine speed increases with the increase of load resistance and there is a maximum value of transmission-generator efficiency with the variation of the turbine speed; when the turbine speed and generator speed keep constant, the transmissiongenerator efficiency decreases and gradually tends to zero with the increase of load resistance.
文摘The aims of this study are to determine the population genetic structure of Rhizoctonia solani,associated with potato,and to assess its resistance degree to pencycuron and thiabendazole fungicides.A total of 57 strains of R.Solani were isolated from different potato crop fields in Mexico,and were classified according to their anastomosis group(AG)using the polymerase chain reaction(PCR)and restriction fragment length polymorphism(RFLP)-based analysis.Then,the amplified fragments were digested with four different endonucleases(Mse I,Ava II,Mun I and Hinc II).The Repetitive Element Sequence-Based PCR(rep-PCR)technique was used to determine the genetic diversity in R.solani populations.Results obtained by PCR-RFLP showed that 81%of the isolates were identified as belonging to AG-3 group,14%to AG1-1B and 5%to AG-11 group.In response to fungicides inhibition,IC_(50)between 0.014-0.039 mg a.i./L for pencycuron,and 0.82 to 2.91 for thiabendazole were determined,This IC_(50)value showed that the resistance factor(RF)values ranged from 1.4 to 3.945 and 0.27 to 0.97,respectively;this tendency suggests that isolates are susceptible to thiabendazole.The AG groups showed a heterogeneous resistance to pencycuron and thiabendazole,being more tolerant to these fungicides AG1-1B and AG-11 groups.The genetic analysis shows a low genetic diversity among(P-value 0.3225)and within(P-value 0.3275)populations;this can indicate a clonal reproduction and little parasexual cycle among the analyzed isolations.