Potassium-ion batteries(PIBs)are considered promising alternatives to lithium-ion batteries owing to cost-effective potassium resources and a suitable redox potential of-2.93 V(vs.-3.04 V for Li+/Li).However,the explo...Potassium-ion batteries(PIBs)are considered promising alternatives to lithium-ion batteries owing to cost-effective potassium resources and a suitable redox potential of-2.93 V(vs.-3.04 V for Li+/Li).However,the exploration of appro-priate electrode materials with the correct size for reversibly accommodating large K+ions presents a significant challenge.In addition,the reaction mecha-nisms and origins of enhanced performance remain elusive.Here,tetragonal FeSe nanoflakes of different sizes are designed to serve as an anode for PIBs,and their live and atomic-scale potassiation/depotassiation mechanisms are revealed for the first time through in situ high-resolution transmission electron micros-copy.We found that FeSe undergoes two distinct structural evolutions,sequen-tially characterized by intercalation and conversion reactions,and the initial intercalation behavior is size-dependent.Apparent expansion induced by the intercalation of K+ions is observed in small-sized FeSe nanoflakes,whereas unexpected cracks are formed along the direction of ionic diffusion in large-sized nanoflakes.The significant stress generation and crack extension originating from the combined effect of mechanical and electrochemical interactions are elucidated by geometric phase analysis and finite-element analysis.Despite the different intercalation behaviors,the formed products of Fe and K_(2)Se after full potassiation can be converted back into the original FeSe phase upon depotassiation.In particular,small-sized nanoflakes exhibit better cycling perfor-mance with well-maintained structural integrity.This article presents the first successful demonstration of atomic-scale visualization that can reveal size-dependent potassiation dynamics.Moreover,it provides valuable guidelines for optimizing the dimensions of electrode materials for advanced PIBs.展开更多
Several significant events of a geological nature occurred approximately 800 ka before the present: (1) Australasian tektite fall (AA), (2) Brunhes-Matuyama geomagnetic reversal (BMR), (3) mid-Pleistocene changes in i...Several significant events of a geological nature occurred approximately 800 ka before the present: (1) Australasian tektite fall (AA), (2) Brunhes-Matuyama geomagnetic reversal (BMR), (3) mid-Pleistocene changes in ice age cycles. Add to these the undated fault system (4) in the South-West (SW) of the South China Sea (SCS). Here we offer a unified cause for all four of these in (5), an impact in the SCS of a large, massive cosmic object, likely a comet, obliquely coming from the SW at an extremely shallow angle, striking the Sunda shelf yet unexploded with the shock of its compressed air bow wave, and causing the continual shelf and slope to collapse, resulting in the fault system (4), then traveling almost tangentially to the surface, exploding at impact with the sea surface, ejecting the tektites (1), creating the formation underlying the later atolls of Spratlies Archipelago (6), Nansha Islands in Chinese, & causing the BMR (2). An explanation of event (3) was Richard Muller’s hypothesis of planet Earth passing through an interplanetary dust cloud periodically due to ecliptic precession. Here we hypothesize this cloud actually is a belt of Australasian tektites ejected into space at super-orbital velocities that Earth encounters about every 100 ka.展开更多
The p27Kip1 is a cell cycle repressor protein that regulates primarily the cell cycle transition from G1 to S phase and hence the DNA replication is in the S phase and cell division in the M phase. Expression of p27Ki...The p27Kip1 is a cell cycle repressor protein that regulates primarily the cell cycle transition from G1 to S phase and hence the DNA replication is in the S phase and cell division in the M phase. Expression of p27Kip1 protein has dual roles for both cancer prevention and promotion. For example, numerous nutritional and chemopreventive anti-cancer agents specifically increase the expression of p27Kip1 protein without directly affecting the expression of any other cell cycle regulatory proteins. On the other hand, pro-cancer agents (like glucose, insulin and other growth factors frequently seen in obesity and/or diabetes) specifically decrease the expression of p27Kip1 protein without directly affecting the expression of any other cell cycle regulatory proteins. Unlike expression of any other cell cycle regulatory proteins, expression of p27Kip1 protein is very unusual. The mRNA of p27Kip1 has a very long and unusual 5’-untranslated region (from -575 to -1 in human). It appears that the 5’-untranslated region of p27Kip1 mRNA forms two alternative secondary structures. One increases the expression of p27Kip1 protein when anti-cancer agents are added and another decrease the expression of p27K1p1 when pro-cancer agents are added. For this short concept proposal, Dr. Albert Einstein’s “visualized thought experiments (German: Gedanken experiment)” were used as a fundamental tool for understanding how either anti- or pro-cancer agents bring the primary structure of the 5’-untranslated region of p27Kip1 mRNA into two alternative secondary structures, thereby either increasing or decreasing, respectively, the translation initiation of p27Kip1 protein.展开更多
Sandstone is the fundamental material in various engineering and construction projects.However,the mechanical integrity of sandstone can be compromised by initial unloading damage resulting from activities such as eng...Sandstone is the fundamental material in various engineering and construction projects.However,the mechanical integrity of sandstone can be compromised by initial unloading damage resulting from activities such as engineering excavations.Furthermore,this degradation is further exacerbated under periodic dry-wet environmental conditions.This study investigated the effects of dry-wet cycles and unloading on the mechanical properties of jointed fine sandstone using uniaxial and triaxial compression tests.These tests were performed on rock samples subjected to varying unloading degrees and different numbers of dry-wet cycles.The results demonstrate that with an increase in the unloading degree from 0%to 70%,there is a corresponding decrease in peak stress ranging from 10%to 33%.Additionally,the cohesion exhibits a reduction of approximately 20%to 25%,while the internal friction angle experiences a decline of about 3.5%to 6%.These findings emphasize a significant unloading effect.Moreover,the degree of peak stress degradation in unloading jointed fine sandstone diminishes with an increase in confining pressure,suggesting that confining pressure mitigates the deterioration caused by dry-wet cycles.Additionally,as the number of dry-wet cycles increases,there is a notable decline in the mechanical properties of the sandstone,evidencing significant dry-wet degradation.Utilizing the Drucker Prager criterion,this study establishes a strength criterion and fracture criterion,denoted as σ_(1)(m,n) and K_(T)^(Ⅱ)(m, n), to quantify the combined impacts of dry-wet cycles and unloading on jointed fine sandstone,which provides a comprehensive understanding of its mechanical behavior under such conditions.展开更多
Underground pumped storage power plant(UPSP)is an innovative concept for space recycling of abandoned mines.Its realization requires better understanding of the dynamic performance and durability of reservoir rock.Thi...Underground pumped storage power plant(UPSP)is an innovative concept for space recycling of abandoned mines.Its realization requires better understanding of the dynamic performance and durability of reservoir rock.This paper conducted ultrasonic detection,split Hopkinson pressure bar(SHPB)impact,mercury intrusion porosimetry(MIP),and backscatter electron observation(BSE)tests to investigate the dynamical behaviour and microstructure of sandstone with cyclical dry-wet damage.A coupling FEM-DEM model was constructed for reappearing mesoscopic structure damage.The results show that dry-wet cycles decrease the dynamic compressive strength(DCS)with a maximum reduction of 39.40%,the elastic limit strength is reduced from 41.75 to 25.62 MPa.The sieved fragments obtain the highest crack growth rate during the 23rd dry-wet cycle with a predictable life of 25 cycles for each rock particle.The pore fractal features of the macropores and micro-meso pores show great differences between the early and late cycles,which verifies the computational statistics analysis of particle deterioration.The numerical results show that the failure patterns are governed by the strain in pre-peak stage and the shear cracks are dominant.The dry-wet cycles reduce the energy transfer efficiency and lead to the discretization of force chain and crack fields.展开更多
In this paper, the performance of a waste rock transportation process in an open pit mine was assessed by using cycle time data. A computerized truck-excavator dispatch system was used to record the cycle times. The p...In this paper, the performance of a waste rock transportation process in an open pit mine was assessed by using cycle time data. A computerized truck-excavator dispatch system was used to record the cycle times. The process was broken into seven steps (or components of the total cycle), durations of which were recorded for a period of 1 month, leading to N = 60,690 data points or dispatches. The open pit mine studied consisted of 12 waste types loaded by 14 excavators and hauled by 49 trucks (at a trucks-to-excavator ratio of 3.5:1) in 75 changing locations. The string-type data was coded using integers to allow a FORTRAN code to extract process performance parameters using statistical analysis. The study established a wide range of parameters including: the waste material generation rate (about 1.73 million t/month, 81% comprising waste rock), truck fill factor, f, total cycle time (Tct), production capacity, theoretical cycle time, non-productive cycle time Tnp, and cycle time performance ratio (CTPR), denoted as Tpr. The factors affecting the process performance include: truck model, excavator model, location (haul distance and road conditions) and material type. For a fixed material type and tonnage, the PDFs of the cycle time components were logarithmic in nature, capable of differentiating performance variations under different factors. It was concluded that the performance of the waste material transportation system in this mine was determined to be acceptable due to mean value of Tpr = 2.432 being closer to unity. Reduction measures were suggested to minimize the cycle time for the process bottlenecks determined from Pareto analysis (that is, full haul, empty haul and loading processes).展开更多
This study presents the effect of excavator model, loading operation location, shift availability and truck-shovel combination on loading cycle time and productivity of an open-pit mine. The loading cycle time was use...This study presents the effect of excavator model, loading operation location, shift availability and truck-shovel combination on loading cycle time and productivity of an open-pit mine. The loading cycle time was used to assess the material loading system performance which is one of the key components of the total cycle time for material transportation in an open-pit mine. Loading is among the components of cycle time during which material is being handled. The data analyzed?was?collected from a computerized dispatch system at GGM from which 62,000 loading dispatches per month involving several shifts, 14 excavators and 49 trucks were loaded. About 4465 dispatches per excavator and 1276 dispatches per truck were assessed using loading cycle time data for each dispatch for a period of four months (between August and December). Under fixed tonnage loaded and waste type (33 t of non-acid forming waste rock),?it was observed that loading cycle time depends on excavator model, location and truck being loaded. Average cycle times, PDFS?and CDFS of loading cycle time series were used to identify differences in performance under different situations. It was concluded that shift availability for excavators, loading location, excavator model and truck-shovel combinations strongly affect the productivity during loading process in an open-pit mine.展开更多
Enzyme-induced carbonate precipitation(EICP)is an emanating,eco-friendly and potentially sound technique that has presented promise in various geotechnical applications.However,the durability and microscopic character...Enzyme-induced carbonate precipitation(EICP)is an emanating,eco-friendly and potentially sound technique that has presented promise in various geotechnical applications.However,the durability and microscopic characteristics of EICP-treated specimens against the impact of drying-wetting(D-W)cycles is under-explored yet.This study investigates the evolution of mechanical behavior and pore charac-teristics of EICP-treated sea sand subjected to D-W cycles.The uniaxial compressive strength(UCS)tests,synchrotron radiation micro-computed tomography(micro-CT),and three-dimensional(3D)recon-struction of CT images were performed to study the multiscale evolution characteristics of EICP-reinforced sea sand under the effect of D-W cycles.The potential correlations between microstructure characteristics and macro-mechanical property deterioration were investigated using gray relational analysis(GRA).Results showed that the UCS of EICP-treated specimens decreases by 63.7% after 15 D-W cycles.The proportion of mesopores gradually decreases whereas the proportion of macropores in-creases due to the exfoliated calcium carbonate with increasing number of D-W cycles.The micro-structure in EICP-reinforced sea sand was gradually disintegrated,resulting in increasing pore size and development of pore shape from ellipsoidal to columnar and branched.The gray relational degree suggested that the weight loss rate and UCS deterioration were attributed to the development of branched pores with a size of 100-1000 m m under the action of D-W cycles.Overall,the results in this study provide a useful guidancee for the long-term stability and evolution characteristics of EICP-reinforced sea sand under D-W weathering conditions.展开更多
Modern metropolises are increasingly affected by air quality problems. Transportation is one of the largest sources of several pollutants emissions, such as nitrogen oxides (NOx) and carbon monoxide (CO). Today in the...Modern metropolises are increasingly affected by air quality problems. Transportation is one of the largest sources of several pollutants emissions, such as nitrogen oxides (NOx) and carbon monoxide (CO). Today in the EU, vehicles' emissions are strictly limited by Euro 6 norm-Euro VI for heavy-duty vehicles-which is periodically upgraded. To match such limits, manufacturers are forced in developing new technologies to perform new sustainable vehicles design strategies, such as EVs and HEVs. Present work's aim is to provide the design of series-hybrid urban transportation bus, equipped with a novel thermal power unit, namely a small gas turbine, to exploit its cleaner combustion process in comparison with an ICE. The control logic is described, while the main drivetrain components are chosen, and suitable models from suppliers are selected as well. Then, some simulations of the resulting vehicle are performed on opportune drive cycles, using Advisor, a free software based on Matlab-Simulink environment, published by US' National Renewable Energy Laboratory (NREL). Two different final configurations are environmentally and economically analysed, with the thermal power unit being respectively fuelled by compressed natural gas (CNG) and liquefied petroleum gas (LPG). Both satisfy the Euro VI norms, showing a substantial emission reduction (-89% and -43% in CO and THC releases respectively) in comparison to pollutants' threshold values.展开更多
Li4Ti5012 (LTO) with rich R-TiO2 (17.06, 23.69, and 34.42 wt%), namely, R-TiO2@Li4Ti5O12 composites, were synthesized using the hydrothermal method and tetrabutyl titanate (TBT) as the precursor. Rietveld refinement o...Li4Ti5012 (LTO) with rich R-TiO2 (17.06, 23.69, and 34.42 wt%), namely, R-TiO2@Li4Ti5O12 composites, were synthesized using the hydrothermal method and tetrabutyl titanate (TBT) as the precursor. Rietveld refinement of X-ray diffraction (XRD) results show that the proportion of Li occupying 16d sites is extraordinary low and the lattice constants of LTO and R-TiO2 change with the ritanium dioxide content. EIS measurements showed that with in creasing R-TiO2 content, both its charge transfer impedance (Rct) and lithium ion diffusion coefficient (DLi) decreased. The changes of Rct and DLi caused by the increase of titanium dioxide content have synergic-antagonistic effects on the rate and cycle properties of Li4Ti5012. The rate performance is positively related to DLi, while the cycle property is negatively correlated with Rct, indicati ng that the rate performs nee is mainly related to DLi, while Rct more significantly affects the cycle performance. LTO-RT-17.06% exhibited excellent rate properties, especially under a high current density (5.0 C, 132.5 mAh/g) and LTO-RT-34.42% showed superior long-term cycle performance (0.012% capacity loss per cycle) compared to that of LTO-RT-17.06% and LTO-RT-23.69%.展开更多
A cradle-to-grave life cycle assessment is done to identify the environmental impacts of chromated copper arsenate (CCA)-treated timber used for highway guard rail posts, to understand the processes that contribute to...A cradle-to-grave life cycle assessment is done to identify the environmental impacts of chromated copper arsenate (CCA)-treated timber used for highway guard rail posts, to understand the processes that contribute to the total impacts, and to determine how the impacts compare to the primary alternative product, galvanized steel posts. Guard rail posts are the supporting structures for highway guard rails. Transportation engineers, as well as public and regulatory interests, have increasing need to understand the environmental implications of guard rail post selection, in addition to factors such as costs and service performance. This study uses a life cycle inventory (LCI) to catalogue the input and output data from guard rail post manufacture, service life, and disposition, and a life cycle impact assessment (LCIA) to assess anthropogenic and net greenhouse gas (GHG), acidification, smog, ecotoxicity, and eutrophication potentially resulting from life cycle air emissions. Other indicators of interest also are tracked, such as fossil fuel and water use. Comparisons of guard rail post products are made at a functional unit of one post per year of service. This life cycle assessment (LCA) finds that the manufacture, use, and disposition of CCA-treated wood guard rails offers lower fossil fuel use and lower anthropogenic and net GHG emissions, acidification, smog potential, and ecotoxicity environmental impacts than impact indicator values for galvanized steel posts. Water use and eutrophication impact indicator values for CCA-treated guard rail posts are greater than impact indicator values for galvanized steel guard rail posts.展开更多
In recent years, there has been global interest in meeting targets relating to energy affordability and security while taking into account greenhouse gas emissions. This has heightened major interest in potential inve...In recent years, there has been global interest in meeting targets relating to energy affordability and security while taking into account greenhouse gas emissions. This has heightened major interest in potential investigations into the use of supercritical carbon dioxide (sCO2) power cycles. Climate change mitigation is the ultimate driver for this increased interest;other relevant issues include the potential for high cycle efficiency and a circular economy. In this study, a 25 MWe recompression closed Brayton cycle (RCBC) has been assessed, and sCO2 has been proposed as the working fluid for the power plant. The methodology used in this research work comprises thermodynamic and techno-economic analysis for the prospective commercialization of this sCO2 power cycle. An evaluated estimation of capital expenditure, operational expenditure, and cost of electricity has been considered in this study. The ASPEN Plus simulation results have been compared with theoretical and mathematical calculations to assess the performance of the compressors, turbine, and heat exchangers. The results thus reveal that the cycle efficiency for this prospective sCO2 recompression closed Brayton cycle increases (39% - 53.6%) as the temperature progressively increases from 550˚C to 900˚C. Data from the Aspen simulation model was used to aid the cost function calculations to estimate the total capital investment cost of the plant. Also, the techno-economic results have shown less cost for purchasing equipment due to fewer components being required for the cycle configuration as compared to the conventional steam power plant.展开更多
Freeze-thaw cycles are closely related to the slope instability in high-altitude mountain regions. In this study, cohesive coarse-grained soils were collected from a high-altitude slope in the Qinghai–Tibet Plateau t...Freeze-thaw cycles are closely related to the slope instability in high-altitude mountain regions. In this study, cohesive coarse-grained soils were collected from a high-altitude slope in the Qinghai–Tibet Plateau to study the effect of cyclic freeze-thaw on their uniaxial mechanical properties. The soil specimens were remolded with three dry densities and three moisture contents. Then, after performing a series of freeze-thaw tests in a closed system without water supply, the soil specimens were subjected to a uniaxial compression test. The results showed that the stress-strain curves of the tested soils mainly performed as strain-softening. The softening feature intensified with the increasing dry density but weakened with an increase in freeze-thaw cycles and moisture content. The uniaxial compressive strength, resilient modulus, residual strength and softening modulus decreased considerably with the increase of freeze-thaw cycles. After more than nine freeze-thaw cycles, these four parameters tended to be stable. These parameters increased with the increase of dry density and decreased with the increasing moisture content, except for the residual strength which did not exhibit any clear variation with an increase in moisture content. The residual strength, however, generally increased with an increase in dry density. The soil structural damage caused by frozen water expansion during the freeze-thaw is the major cause for the changes in mechanical behaviors of cohesive coarse-grained soils. With results in this study, the deterioration effect of freeze-thaw cycles on the mechanical properties of soils should be considered during the slope stability analysis in high-altitude mountain regions.展开更多
The menstrual cycle has been a topic of interest in relation to behavior and cognition for many years, with historical beliefs associating it with cognitive impairment. However, recent research has challenged these be...The menstrual cycle has been a topic of interest in relation to behavior and cognition for many years, with historical beliefs associating it with cognitive impairment. However, recent research has challenged these beliefs and suggested potential positive effects of the menstrual cycle on cognitive performance. Despite these emerging findings, there is still a lack of consensus regarding the impact of the menstrual cycle on cognition, particularly in domains such as spatial reasoning, visual memory, and numerical memory. Hence, this study aimed to explore the relationship between the menstrual cycle and cognitive performance in these specific domains. Previous studies have reported mixed findings, with some suggesting no significant association and others indicating potential differences across the menstrual cycle. To contribute to this body of knowledge, we explored the research question of whether the menstrual cycles have a significant effect on cognition, particularly in the domains of spatial reasoning, visual and numerical memory in a regionally diverse sample of menstruating females. A total of 30 menstruating females from mixed geographical backgrounds participated in the study, and a repeated measures design was used to assess their cognitive performance in two phases of the menstrual cycle: follicular and luteal. The results of the study revealed that while spatial reasoning was not significantly related to the menstrual cycle (p = 0.256), both visual and numerical memory had significant positive associations (p < 0.001) with the luteal phase. However, since the effect sizes were very small, the importance of this relationship might be commonly overestimated. Future studies could thus entail designs with larger sample sizes, including neuro-biological measures of menstrual stages, and consequently inform competent interventions and support systems.展开更多
The internal curing effect of superabsorbent polymer(SAP) on the properties of high performance concrete(HPC) under marine wetting and drying cycles(WD cycles) was investigated. Compressive strength, hydration and chl...The internal curing effect of superabsorbent polymer(SAP) on the properties of high performance concrete(HPC) under marine wetting and drying cycles(WD cycles) was investigated. Compressive strength, hydration and chloride migration were experimentally investigated and the results were evaluated by compasison with those under fresh water curing(FW). Water absorption and porosity were also evaluated only under WD cycles. The results showed the important influence of wetting and drying cycles on the properties of SAP modified HPC properties. Carefully designed, SAP minimized the long-term compressive strength of HPC under marine WD cycles. The hydration rate was faster in the initial curing, but became lower as compared with that cured in FW. In addition, SAP improved the long-term water absorption resistance and chloride migration resistance of HPC under marine WD cycles. The examination of the porosity showed a lower increase of the volume of capillary pores in SAP modified HPC under long term WD cycles compared with that without SAP. Therefore, internal curing by SAP could improve the durability properties of HPC under marine WD cycles.展开更多
Neurodegenerative diseases are caused by the progressive loss of specific neurons.The exact mechanisms of action of these diseases are unknown,and many studies have focused on pathways related to abnormal accumulation...Neurodegenerative diseases are caused by the progressive loss of specific neurons.The exact mechanisms of action of these diseases are unknown,and many studies have focused on pathways related to abnormal accumulation and processing of proteins,mitochondrial dysfunction,and oxidative stress leading to apoptotic death.However,a growing body of evidence indicates that aberrant cell cycle re-entry plays a major role in the pathogenesis of neurodegeneration.The activation of the cell cycle in mature neurons could be promoted by several signaling mechanisms,including c-Jun N-terminal kinases,p38 mitogen-activated protein kinases,and mitogen-activated protein kinase/extracellular signal-regulated kinase cascades;post-translational modifications such as Tau-phosphorylation;and DNA damage response.In all these events,implicated Cdk5,a proline-directed serine/threonine protein kinase,seems to be responsible for several cellular processes in neurons including axon growth,neurotransmission,synaptic plasticity,neuronal migration,and maintenance of neuronal survival.However,under pathological conditions,Cdk5 dysregulation may lead to cell cycle re-entry in post-mitotic neurons.Thus,Cdk5 hyperactivation,by its physiologic activator p25,hyper-phosphorylates downstream substrates related to neurodegenerative diseases.This review summarizes factors such as oxidative stress,DNA damage response,signaling pathway disturbance,and Ubiquitin proteasome malfunction contributing to cell cycle re-entry in post-mitotic neurons.It also describes how all these factors are linked to a greater or lesser extent with Cdk5.Thus,it offers a global vision of the function of cell cycle-related proteins in mature neurons with a focus on Cdk5 and how this protein contributes to the development of Alzheimer’s disease,Parkinson’s disease,amyotrophic lateral sclerosis,and Huntington’s disease by cell cycle activation.展开更多
AIM: To determine the effect of cis -9, trans -11-conjugated linoleic acid (c9, t11-CLA) on the cell cycle of gastric cancer cells (SGC-7901) and its possible mechanism in inhibition cancer growth. METHODS: Using cell...AIM: To determine the effect of cis -9, trans -11-conjugated linoleic acid (c9, t11-CLA) on the cell cycle of gastric cancer cells (SGC-7901) and its possible mechanism in inhibition cancer growth. METHODS: Using cell culture and immunocytochemical techniques, we examined the cell growth, DNA synthesis, expression of PCNA, cyclin A, B(1), D(1), p16(ink4a) and p21(cip/waf1) of SGC-7901 cells which were treated with various c9, t11-CLA concentrations (25, 50, 100 and 200 micromol.L(-1))of c 9, t 11-CLA for 24 and 48h, with a negative control (0.1% ethane). RESULTS: The cell growth and DNA synthesis of SGC-7901 cells were inhibited by c9, t11-CLA.SGC-7901 cells. Eight day after treatment with various concentrations of c9, t11-CLA mentioned above, the inhibition rates were 5.92%, 20.15%, 75.61% and 82.44%, respectively and inhibitory effect of c9, t11-CLA on DNA synthesis (except for 25 micromol.L, 24h) showed significantly less (3)H-TdR incorporation than that in the negative controls (P【0.05 and P【0.01). Immunocytochemical staining demonstrated that SGC-7901 cells preincubated in media supplemented with different c9, t11-CLA concentrations at various times significantly decreased the expressions of PCNA (the expression rates were 7.2-3.0%, 24h and 9.1-0.9% at 48h, respectively), Cyclin A (11.0-2.3%, 24h and 8.5-0.5%,48h), B(1) (4.8-1.8% at 24h and 5.5-0.6% at 48h)and D(1) (3.6-1.4% at 24h and 3.7%-0 at 48h) as compared with those in the negative controls(the expressions of PCNA, Cyclin A, B(1) and D(1) were 6.5% at 24h and 9.0% at 48h, 4.2% at 24h and 5.1% at 48h, 9.5% at 24h and 6.0% at 48h,respectively)(P【0.01), whereas the expressions of P16(ink4a) and P21(cip/waf1), cyclin-dependent kinases inhibitors(CDKI), were increased. CONCLUSION: The cell growth and proliferation of SGC-7901 cell is inhibited by c9, t11-CLA via blocking the cell cycle, with reduced expressions of cyclin A,B(1) and D(1) and enhanced expressions of CDKI(P16(ink4a) and p21(cip/waf1)).展开更多
With an analysis of zonal wind observations over 40 years, Salby and Callaghan [1] showed that the Quasi-biennial Oscillation (QBO) at 20 km is modulated by 11-year solar cycle (SC) variations from about 12 to 20 m/s ...With an analysis of zonal wind observations over 40 years, Salby and Callaghan [1] showed that the Quasi-biennial Oscillation (QBO) at 20 km is modulated by 11-year solar cycle (SC) variations from about 12 to 20 m/s (Figure 2). The observations are reproduced qualitatively in a study with the 3D Numerical Spectral Model, which shows that the SC effect of the stratospheric QBO is produced by dynamical downward coupling originating in the mesosphere. In this modeling study, the SC period is taken to be 10 years, and a realistic heat source is applied varying exponentially with altitude: 0.2%, surface;2%, 50 km;20%, 100 km and above. The numerical results show that the variable solar radiation in the mesosphere around 65 km generates a hemispheric symmetric Equatorial Annual Oscillation (EAO), which is modulated by relatively large SC variations. Under the influence of wave mean flow interactions, the EAO propagates into the lower atmosphere and is the dynamical source or pacemaker for the large SC modulation of the QBO. The numerical results show that the upward propagating small-scale gravity waves from the troposphere amplify the SC modulations of the QBO and EAO in the stratosphere, part of the SC mechanism. The zonal winds of the equatorial QBO and EAO produce through the meridional circulation measurable SC variations in the temperature of the stratosphere and troposphere at high latitudes. Analysis of NCEP temperature and zonal wind data (1958 to 2006) provides observational evidence of the EAO with SC variations around 11 years.展开更多
Effective calcium(Ca)management is crucial for optimizing oil palm cultivation and enhancing crop yield.This study aimed to gain insights into the dynamics of Ca concentration,accumulation,exportation,immobilization,a...Effective calcium(Ca)management is crucial for optimizing oil palm cultivation and enhancing crop yield.This study aimed to gain insights into the dynamics of Ca concentration,accumulation,exportation,immobilization,and recycling in various oil palm organs relative to plant age.The experiment was conducted at the Agropalma enterprise site in the northeastern region of Para State,Brazil,evaluating seven plant age treatments:2,3,4,5,6,7,and 8 years old.Employing a completely randomized design with four replications.The results demonstrated an age-related increase in Ca concentration in petioles,rachis,arrows,male inflorescences,peduncles,and fruits.Furthermore,Ca accumulation exhibited an upward trend in all organs with progressing plant age.Notably,the study revealed an enhanced Ca use efficiency across all plant organs in correlation with the age of oil palm cultivation.These findings underscore the dynamic nutritional demands of oil palm,influencing Ca immobilization,cycling,and export throughout its developmental stages.展开更多
The influence of hydrogen embrittlement on the fatigue behaviors of AISI 304 stainless steel is investigated. The fatigue endurance limits of the untreated and hydrogen-embrittled materials were almost the same at 400...The influence of hydrogen embrittlement on the fatigue behaviors of AISI 304 stainless steel is investigated. The fatigue endurance limits of the untreated and hydrogen-embrittled materials were almost the same at 400 MPa, and hydrogen embrittlement had little influence even though the sample contained about 8.1 times more hydrogen. Thus, the sensitivity of hydrogen gas in this material is very low. A surface crack initiation, growth, coalescence, and micro ridge model is proposed in this study. Slip line formation?⇒microcrack formation?⇒increases in the crack width, and blunting of the crack tip as it grows?⇒formation of many slip lines because of deformation in the shear direction?⇒growth of the crack in the shear direction, forming micro ridges, coalescence with adjacent cracks ⇒?continuous initiation, growth, coalescence, and ridge formation of surface cracks and specimen breakage.展开更多
基金This work was supported by the National Key R&D Program of China(Grant No.2018YFB1304902)the National Natural Science Foundation of China(Grant Nos.12004034,U1813211,22005247,11904372,51502007,52072323,52122211,12174019,and 51972058)+1 种基金the Gen-eral Research Fund of Hong Kong(Project No.11217221)China Postdoctoral Science Foundation Funded Project(Grant No.2021M690386).
文摘Potassium-ion batteries(PIBs)are considered promising alternatives to lithium-ion batteries owing to cost-effective potassium resources and a suitable redox potential of-2.93 V(vs.-3.04 V for Li+/Li).However,the exploration of appro-priate electrode materials with the correct size for reversibly accommodating large K+ions presents a significant challenge.In addition,the reaction mecha-nisms and origins of enhanced performance remain elusive.Here,tetragonal FeSe nanoflakes of different sizes are designed to serve as an anode for PIBs,and their live and atomic-scale potassiation/depotassiation mechanisms are revealed for the first time through in situ high-resolution transmission electron micros-copy.We found that FeSe undergoes two distinct structural evolutions,sequen-tially characterized by intercalation and conversion reactions,and the initial intercalation behavior is size-dependent.Apparent expansion induced by the intercalation of K+ions is observed in small-sized FeSe nanoflakes,whereas unexpected cracks are formed along the direction of ionic diffusion in large-sized nanoflakes.The significant stress generation and crack extension originating from the combined effect of mechanical and electrochemical interactions are elucidated by geometric phase analysis and finite-element analysis.Despite the different intercalation behaviors,the formed products of Fe and K_(2)Se after full potassiation can be converted back into the original FeSe phase upon depotassiation.In particular,small-sized nanoflakes exhibit better cycling perfor-mance with well-maintained structural integrity.This article presents the first successful demonstration of atomic-scale visualization that can reveal size-dependent potassiation dynamics.Moreover,it provides valuable guidelines for optimizing the dimensions of electrode materials for advanced PIBs.
文摘Several significant events of a geological nature occurred approximately 800 ka before the present: (1) Australasian tektite fall (AA), (2) Brunhes-Matuyama geomagnetic reversal (BMR), (3) mid-Pleistocene changes in ice age cycles. Add to these the undated fault system (4) in the South-West (SW) of the South China Sea (SCS). Here we offer a unified cause for all four of these in (5), an impact in the SCS of a large, massive cosmic object, likely a comet, obliquely coming from the SW at an extremely shallow angle, striking the Sunda shelf yet unexploded with the shock of its compressed air bow wave, and causing the continual shelf and slope to collapse, resulting in the fault system (4), then traveling almost tangentially to the surface, exploding at impact with the sea surface, ejecting the tektites (1), creating the formation underlying the later atolls of Spratlies Archipelago (6), Nansha Islands in Chinese, & causing the BMR (2). An explanation of event (3) was Richard Muller’s hypothesis of planet Earth passing through an interplanetary dust cloud periodically due to ecliptic precession. Here we hypothesize this cloud actually is a belt of Australasian tektites ejected into space at super-orbital velocities that Earth encounters about every 100 ka.
文摘The p27Kip1 is a cell cycle repressor protein that regulates primarily the cell cycle transition from G1 to S phase and hence the DNA replication is in the S phase and cell division in the M phase. Expression of p27Kip1 protein has dual roles for both cancer prevention and promotion. For example, numerous nutritional and chemopreventive anti-cancer agents specifically increase the expression of p27Kip1 protein without directly affecting the expression of any other cell cycle regulatory proteins. On the other hand, pro-cancer agents (like glucose, insulin and other growth factors frequently seen in obesity and/or diabetes) specifically decrease the expression of p27Kip1 protein without directly affecting the expression of any other cell cycle regulatory proteins. Unlike expression of any other cell cycle regulatory proteins, expression of p27Kip1 protein is very unusual. The mRNA of p27Kip1 has a very long and unusual 5’-untranslated region (from -575 to -1 in human). It appears that the 5’-untranslated region of p27Kip1 mRNA forms two alternative secondary structures. One increases the expression of p27Kip1 protein when anti-cancer agents are added and another decrease the expression of p27K1p1 when pro-cancer agents are added. For this short concept proposal, Dr. Albert Einstein’s “visualized thought experiments (German: Gedanken experiment)” were used as a fundamental tool for understanding how either anti- or pro-cancer agents bring the primary structure of the 5’-untranslated region of p27Kip1 mRNA into two alternative secondary structures, thereby either increasing or decreasing, respectively, the translation initiation of p27Kip1 protein.
基金financially supported by the National Natural Science Foundation of China(42177166).
文摘Sandstone is the fundamental material in various engineering and construction projects.However,the mechanical integrity of sandstone can be compromised by initial unloading damage resulting from activities such as engineering excavations.Furthermore,this degradation is further exacerbated under periodic dry-wet environmental conditions.This study investigated the effects of dry-wet cycles and unloading on the mechanical properties of jointed fine sandstone using uniaxial and triaxial compression tests.These tests were performed on rock samples subjected to varying unloading degrees and different numbers of dry-wet cycles.The results demonstrate that with an increase in the unloading degree from 0%to 70%,there is a corresponding decrease in peak stress ranging from 10%to 33%.Additionally,the cohesion exhibits a reduction of approximately 20%to 25%,while the internal friction angle experiences a decline of about 3.5%to 6%.These findings emphasize a significant unloading effect.Moreover,the degree of peak stress degradation in unloading jointed fine sandstone diminishes with an increase in confining pressure,suggesting that confining pressure mitigates the deterioration caused by dry-wet cycles.Additionally,as the number of dry-wet cycles increases,there is a notable decline in the mechanical properties of the sandstone,evidencing significant dry-wet degradation.Utilizing the Drucker Prager criterion,this study establishes a strength criterion and fracture criterion,denoted as σ_(1)(m,n) and K_(T)^(Ⅱ)(m, n), to quantify the combined impacts of dry-wet cycles and unloading on jointed fine sandstone,which provides a comprehensive understanding of its mechanical behavior under such conditions.
基金the National Natural Science Foundation of China(Nos.52374147,42372328,and U23B2091)National Key Research and Development Program of China(No.2023YFC3804200)Xinjiang Uygur Autonomous Region Science and Technology Major Program(No.2023A01002).
文摘Underground pumped storage power plant(UPSP)is an innovative concept for space recycling of abandoned mines.Its realization requires better understanding of the dynamic performance and durability of reservoir rock.This paper conducted ultrasonic detection,split Hopkinson pressure bar(SHPB)impact,mercury intrusion porosimetry(MIP),and backscatter electron observation(BSE)tests to investigate the dynamical behaviour and microstructure of sandstone with cyclical dry-wet damage.A coupling FEM-DEM model was constructed for reappearing mesoscopic structure damage.The results show that dry-wet cycles decrease the dynamic compressive strength(DCS)with a maximum reduction of 39.40%,the elastic limit strength is reduced from 41.75 to 25.62 MPa.The sieved fragments obtain the highest crack growth rate during the 23rd dry-wet cycle with a predictable life of 25 cycles for each rock particle.The pore fractal features of the macropores and micro-meso pores show great differences between the early and late cycles,which verifies the computational statistics analysis of particle deterioration.The numerical results show that the failure patterns are governed by the strain in pre-peak stage and the shear cracks are dominant.The dry-wet cycles reduce the energy transfer efficiency and lead to the discretization of force chain and crack fields.
文摘In this paper, the performance of a waste rock transportation process in an open pit mine was assessed by using cycle time data. A computerized truck-excavator dispatch system was used to record the cycle times. The process was broken into seven steps (or components of the total cycle), durations of which were recorded for a period of 1 month, leading to N = 60,690 data points or dispatches. The open pit mine studied consisted of 12 waste types loaded by 14 excavators and hauled by 49 trucks (at a trucks-to-excavator ratio of 3.5:1) in 75 changing locations. The string-type data was coded using integers to allow a FORTRAN code to extract process performance parameters using statistical analysis. The study established a wide range of parameters including: the waste material generation rate (about 1.73 million t/month, 81% comprising waste rock), truck fill factor, f, total cycle time (Tct), production capacity, theoretical cycle time, non-productive cycle time Tnp, and cycle time performance ratio (CTPR), denoted as Tpr. The factors affecting the process performance include: truck model, excavator model, location (haul distance and road conditions) and material type. For a fixed material type and tonnage, the PDFs of the cycle time components were logarithmic in nature, capable of differentiating performance variations under different factors. It was concluded that the performance of the waste material transportation system in this mine was determined to be acceptable due to mean value of Tpr = 2.432 being closer to unity. Reduction measures were suggested to minimize the cycle time for the process bottlenecks determined from Pareto analysis (that is, full haul, empty haul and loading processes).
文摘This study presents the effect of excavator model, loading operation location, shift availability and truck-shovel combination on loading cycle time and productivity of an open-pit mine. The loading cycle time was used to assess the material loading system performance which is one of the key components of the total cycle time for material transportation in an open-pit mine. Loading is among the components of cycle time during which material is being handled. The data analyzed?was?collected from a computerized dispatch system at GGM from which 62,000 loading dispatches per month involving several shifts, 14 excavators and 49 trucks were loaded. About 4465 dispatches per excavator and 1276 dispatches per truck were assessed using loading cycle time data for each dispatch for a period of four months (between August and December). Under fixed tonnage loaded and waste type (33 t of non-acid forming waste rock),?it was observed that loading cycle time depends on excavator model, location and truck being loaded. Average cycle times, PDFS?and CDFS of loading cycle time series were used to identify differences in performance under different situations. It was concluded that shift availability for excavators, loading location, excavator model and truck-shovel combinations strongly affect the productivity during loading process in an open-pit mine.
基金The authors gratefully acknowledge the financial support of National NaturalScience Foundation of China(Grant No.41972276)Natural Science Foundation of Fujian Province,China(Grant No.2020J06013)"Foal Eagle Program"Youth Top-notch Talent Project of Fujian Province,China(Grant No.00387088).
文摘Enzyme-induced carbonate precipitation(EICP)is an emanating,eco-friendly and potentially sound technique that has presented promise in various geotechnical applications.However,the durability and microscopic characteristics of EICP-treated specimens against the impact of drying-wetting(D-W)cycles is under-explored yet.This study investigates the evolution of mechanical behavior and pore charac-teristics of EICP-treated sea sand subjected to D-W cycles.The uniaxial compressive strength(UCS)tests,synchrotron radiation micro-computed tomography(micro-CT),and three-dimensional(3D)recon-struction of CT images were performed to study the multiscale evolution characteristics of EICP-reinforced sea sand under the effect of D-W cycles.The potential correlations between microstructure characteristics and macro-mechanical property deterioration were investigated using gray relational analysis(GRA).Results showed that the UCS of EICP-treated specimens decreases by 63.7% after 15 D-W cycles.The proportion of mesopores gradually decreases whereas the proportion of macropores in-creases due to the exfoliated calcium carbonate with increasing number of D-W cycles.The micro-structure in EICP-reinforced sea sand was gradually disintegrated,resulting in increasing pore size and development of pore shape from ellipsoidal to columnar and branched.The gray relational degree suggested that the weight loss rate and UCS deterioration were attributed to the development of branched pores with a size of 100-1000 m m under the action of D-W cycles.Overall,the results in this study provide a useful guidancee for the long-term stability and evolution characteristics of EICP-reinforced sea sand under D-W weathering conditions.
文摘Modern metropolises are increasingly affected by air quality problems. Transportation is one of the largest sources of several pollutants emissions, such as nitrogen oxides (NOx) and carbon monoxide (CO). Today in the EU, vehicles' emissions are strictly limited by Euro 6 norm-Euro VI for heavy-duty vehicles-which is periodically upgraded. To match such limits, manufacturers are forced in developing new technologies to perform new sustainable vehicles design strategies, such as EVs and HEVs. Present work's aim is to provide the design of series-hybrid urban transportation bus, equipped with a novel thermal power unit, namely a small gas turbine, to exploit its cleaner combustion process in comparison with an ICE. The control logic is described, while the main drivetrain components are chosen, and suitable models from suppliers are selected as well. Then, some simulations of the resulting vehicle are performed on opportune drive cycles, using Advisor, a free software based on Matlab-Simulink environment, published by US' National Renewable Energy Laboratory (NREL). Two different final configurations are environmentally and economically analysed, with the thermal power unit being respectively fuelled by compressed natural gas (CNG) and liquefied petroleum gas (LPG). Both satisfy the Euro VI norms, showing a substantial emission reduction (-89% and -43% in CO and THC releases respectively) in comparison to pollutants' threshold values.
基金financially supported by the National Natural Science Foundation of China(No.51641206)Shandong Natural Science Foundation Project(No.ZR2015EM013)+1 种基金Special Funds for Independent Innovation and Transformation of Achievements in Shandong Province(No.2014CGZH0911)National Key R&D Program of China(No.2016YFB0100508)
文摘Li4Ti5012 (LTO) with rich R-TiO2 (17.06, 23.69, and 34.42 wt%), namely, R-TiO2@Li4Ti5O12 composites, were synthesized using the hydrothermal method and tetrabutyl titanate (TBT) as the precursor. Rietveld refinement of X-ray diffraction (XRD) results show that the proportion of Li occupying 16d sites is extraordinary low and the lattice constants of LTO and R-TiO2 change with the ritanium dioxide content. EIS measurements showed that with in creasing R-TiO2 content, both its charge transfer impedance (Rct) and lithium ion diffusion coefficient (DLi) decreased. The changes of Rct and DLi caused by the increase of titanium dioxide content have synergic-antagonistic effects on the rate and cycle properties of Li4Ti5012. The rate performance is positively related to DLi, while the cycle property is negatively correlated with Rct, indicati ng that the rate performs nee is mainly related to DLi, while Rct more significantly affects the cycle performance. LTO-RT-17.06% exhibited excellent rate properties, especially under a high current density (5.0 C, 132.5 mAh/g) and LTO-RT-34.42% showed superior long-term cycle performance (0.012% capacity loss per cycle) compared to that of LTO-RT-17.06% and LTO-RT-23.69%.
文摘A cradle-to-grave life cycle assessment is done to identify the environmental impacts of chromated copper arsenate (CCA)-treated timber used for highway guard rail posts, to understand the processes that contribute to the total impacts, and to determine how the impacts compare to the primary alternative product, galvanized steel posts. Guard rail posts are the supporting structures for highway guard rails. Transportation engineers, as well as public and regulatory interests, have increasing need to understand the environmental implications of guard rail post selection, in addition to factors such as costs and service performance. This study uses a life cycle inventory (LCI) to catalogue the input and output data from guard rail post manufacture, service life, and disposition, and a life cycle impact assessment (LCIA) to assess anthropogenic and net greenhouse gas (GHG), acidification, smog, ecotoxicity, and eutrophication potentially resulting from life cycle air emissions. Other indicators of interest also are tracked, such as fossil fuel and water use. Comparisons of guard rail post products are made at a functional unit of one post per year of service. This life cycle assessment (LCA) finds that the manufacture, use, and disposition of CCA-treated wood guard rails offers lower fossil fuel use and lower anthropogenic and net GHG emissions, acidification, smog potential, and ecotoxicity environmental impacts than impact indicator values for galvanized steel posts. Water use and eutrophication impact indicator values for CCA-treated guard rail posts are greater than impact indicator values for galvanized steel guard rail posts.
文摘In recent years, there has been global interest in meeting targets relating to energy affordability and security while taking into account greenhouse gas emissions. This has heightened major interest in potential investigations into the use of supercritical carbon dioxide (sCO2) power cycles. Climate change mitigation is the ultimate driver for this increased interest;other relevant issues include the potential for high cycle efficiency and a circular economy. In this study, a 25 MWe recompression closed Brayton cycle (RCBC) has been assessed, and sCO2 has been proposed as the working fluid for the power plant. The methodology used in this research work comprises thermodynamic and techno-economic analysis for the prospective commercialization of this sCO2 power cycle. An evaluated estimation of capital expenditure, operational expenditure, and cost of electricity has been considered in this study. The ASPEN Plus simulation results have been compared with theoretical and mathematical calculations to assess the performance of the compressors, turbine, and heat exchangers. The results thus reveal that the cycle efficiency for this prospective sCO2 recompression closed Brayton cycle increases (39% - 53.6%) as the temperature progressively increases from 550˚C to 900˚C. Data from the Aspen simulation model was used to aid the cost function calculations to estimate the total capital investment cost of the plant. Also, the techno-economic results have shown less cost for purchasing equipment due to fewer components being required for the cycle configuration as compared to the conventional steam power plant.
基金supported by the National Key R&D Program of China (Grant No. 2018YFC1505001)the Key Scientific Research Project of China Gold Group (Grant No. 2016ZGHJ/XZHTL-YQSC-26)+1 种基金the funding from the Department of Transportation of Gansu Province (Grant No. 2017-008)the Fundamental Research Funds for the Central Universities, CHD (Grant No. 300102268716)
文摘Freeze-thaw cycles are closely related to the slope instability in high-altitude mountain regions. In this study, cohesive coarse-grained soils were collected from a high-altitude slope in the Qinghai–Tibet Plateau to study the effect of cyclic freeze-thaw on their uniaxial mechanical properties. The soil specimens were remolded with three dry densities and three moisture contents. Then, after performing a series of freeze-thaw tests in a closed system without water supply, the soil specimens were subjected to a uniaxial compression test. The results showed that the stress-strain curves of the tested soils mainly performed as strain-softening. The softening feature intensified with the increasing dry density but weakened with an increase in freeze-thaw cycles and moisture content. The uniaxial compressive strength, resilient modulus, residual strength and softening modulus decreased considerably with the increase of freeze-thaw cycles. After more than nine freeze-thaw cycles, these four parameters tended to be stable. These parameters increased with the increase of dry density and decreased with the increasing moisture content, except for the residual strength which did not exhibit any clear variation with an increase in moisture content. The residual strength, however, generally increased with an increase in dry density. The soil structural damage caused by frozen water expansion during the freeze-thaw is the major cause for the changes in mechanical behaviors of cohesive coarse-grained soils. With results in this study, the deterioration effect of freeze-thaw cycles on the mechanical properties of soils should be considered during the slope stability analysis in high-altitude mountain regions.
文摘The menstrual cycle has been a topic of interest in relation to behavior and cognition for many years, with historical beliefs associating it with cognitive impairment. However, recent research has challenged these beliefs and suggested potential positive effects of the menstrual cycle on cognitive performance. Despite these emerging findings, there is still a lack of consensus regarding the impact of the menstrual cycle on cognition, particularly in domains such as spatial reasoning, visual memory, and numerical memory. Hence, this study aimed to explore the relationship between the menstrual cycle and cognitive performance in these specific domains. Previous studies have reported mixed findings, with some suggesting no significant association and others indicating potential differences across the menstrual cycle. To contribute to this body of knowledge, we explored the research question of whether the menstrual cycles have a significant effect on cognition, particularly in the domains of spatial reasoning, visual and numerical memory in a regionally diverse sample of menstruating females. A total of 30 menstruating females from mixed geographical backgrounds participated in the study, and a repeated measures design was used to assess their cognitive performance in two phases of the menstrual cycle: follicular and luteal. The results of the study revealed that while spatial reasoning was not significantly related to the menstrual cycle (p = 0.256), both visual and numerical memory had significant positive associations (p < 0.001) with the luteal phase. However, since the effect sizes were very small, the importance of this relationship might be commonly overestimated. Future studies could thus entail designs with larger sample sizes, including neuro-biological measures of menstrual stages, and consequently inform competent interventions and support systems.
基金Funded by National Key Research and Development Program of China(No.2017YFB0310000)Opening Project of State Key Laboratory of Green Building Materials(No.YA-584)the Key Technology Innovation Program from the Ministry of Science and Technology(Hubei Province)(No.2018AAA004)
文摘The internal curing effect of superabsorbent polymer(SAP) on the properties of high performance concrete(HPC) under marine wetting and drying cycles(WD cycles) was investigated. Compressive strength, hydration and chloride migration were experimentally investigated and the results were evaluated by compasison with those under fresh water curing(FW). Water absorption and porosity were also evaluated only under WD cycles. The results showed the important influence of wetting and drying cycles on the properties of SAP modified HPC properties. Carefully designed, SAP minimized the long-term compressive strength of HPC under marine WD cycles. The hydration rate was faster in the initial curing, but became lower as compared with that cured in FW. In addition, SAP improved the long-term water absorption resistance and chloride migration resistance of HPC under marine WD cycles. The examination of the porosity showed a lower increase of the volume of capillary pores in SAP modified HPC under long term WD cycles compared with that without SAP. Therefore, internal curing by SAP could improve the durability properties of HPC under marine WD cycles.
基金supported by the Spanish Ministry of Industry and Competitiveness[Grant BFU2016-80006-P]The Andalusian Regional Government[Group BIO-216]the FEDER-Andalusian programme 2014-2020[1262530-R].
文摘Neurodegenerative diseases are caused by the progressive loss of specific neurons.The exact mechanisms of action of these diseases are unknown,and many studies have focused on pathways related to abnormal accumulation and processing of proteins,mitochondrial dysfunction,and oxidative stress leading to apoptotic death.However,a growing body of evidence indicates that aberrant cell cycle re-entry plays a major role in the pathogenesis of neurodegeneration.The activation of the cell cycle in mature neurons could be promoted by several signaling mechanisms,including c-Jun N-terminal kinases,p38 mitogen-activated protein kinases,and mitogen-activated protein kinase/extracellular signal-regulated kinase cascades;post-translational modifications such as Tau-phosphorylation;and DNA damage response.In all these events,implicated Cdk5,a proline-directed serine/threonine protein kinase,seems to be responsible for several cellular processes in neurons including axon growth,neurotransmission,synaptic plasticity,neuronal migration,and maintenance of neuronal survival.However,under pathological conditions,Cdk5 dysregulation may lead to cell cycle re-entry in post-mitotic neurons.Thus,Cdk5 hyperactivation,by its physiologic activator p25,hyper-phosphorylates downstream substrates related to neurodegenerative diseases.This review summarizes factors such as oxidative stress,DNA damage response,signaling pathway disturbance,and Ubiquitin proteasome malfunction contributing to cell cycle re-entry in post-mitotic neurons.It also describes how all these factors are linked to a greater or lesser extent with Cdk5.Thus,it offers a global vision of the function of cell cycle-related proteins in mature neurons with a focus on Cdk5 and how this protein contributes to the development of Alzheimer’s disease,Parkinson’s disease,amyotrophic lateral sclerosis,and Huntington’s disease by cell cycle activation.
基金the National Natural Science Foundation of China,No.39870661
文摘AIM: To determine the effect of cis -9, trans -11-conjugated linoleic acid (c9, t11-CLA) on the cell cycle of gastric cancer cells (SGC-7901) and its possible mechanism in inhibition cancer growth. METHODS: Using cell culture and immunocytochemical techniques, we examined the cell growth, DNA synthesis, expression of PCNA, cyclin A, B(1), D(1), p16(ink4a) and p21(cip/waf1) of SGC-7901 cells which were treated with various c9, t11-CLA concentrations (25, 50, 100 and 200 micromol.L(-1))of c 9, t 11-CLA for 24 and 48h, with a negative control (0.1% ethane). RESULTS: The cell growth and DNA synthesis of SGC-7901 cells were inhibited by c9, t11-CLA.SGC-7901 cells. Eight day after treatment with various concentrations of c9, t11-CLA mentioned above, the inhibition rates were 5.92%, 20.15%, 75.61% and 82.44%, respectively and inhibitory effect of c9, t11-CLA on DNA synthesis (except for 25 micromol.L, 24h) showed significantly less (3)H-TdR incorporation than that in the negative controls (P【0.05 and P【0.01). Immunocytochemical staining demonstrated that SGC-7901 cells preincubated in media supplemented with different c9, t11-CLA concentrations at various times significantly decreased the expressions of PCNA (the expression rates were 7.2-3.0%, 24h and 9.1-0.9% at 48h, respectively), Cyclin A (11.0-2.3%, 24h and 8.5-0.5%,48h), B(1) (4.8-1.8% at 24h and 5.5-0.6% at 48h)and D(1) (3.6-1.4% at 24h and 3.7%-0 at 48h) as compared with those in the negative controls(the expressions of PCNA, Cyclin A, B(1) and D(1) were 6.5% at 24h and 9.0% at 48h, 4.2% at 24h and 5.1% at 48h, 9.5% at 24h and 6.0% at 48h,respectively)(P【0.01), whereas the expressions of P16(ink4a) and P21(cip/waf1), cyclin-dependent kinases inhibitors(CDKI), were increased. CONCLUSION: The cell growth and proliferation of SGC-7901 cell is inhibited by c9, t11-CLA via blocking the cell cycle, with reduced expressions of cyclin A,B(1) and D(1) and enhanced expressions of CDKI(P16(ink4a) and p21(cip/waf1)).
文摘With an analysis of zonal wind observations over 40 years, Salby and Callaghan [1] showed that the Quasi-biennial Oscillation (QBO) at 20 km is modulated by 11-year solar cycle (SC) variations from about 12 to 20 m/s (Figure 2). The observations are reproduced qualitatively in a study with the 3D Numerical Spectral Model, which shows that the SC effect of the stratospheric QBO is produced by dynamical downward coupling originating in the mesosphere. In this modeling study, the SC period is taken to be 10 years, and a realistic heat source is applied varying exponentially with altitude: 0.2%, surface;2%, 50 km;20%, 100 km and above. The numerical results show that the variable solar radiation in the mesosphere around 65 km generates a hemispheric symmetric Equatorial Annual Oscillation (EAO), which is modulated by relatively large SC variations. Under the influence of wave mean flow interactions, the EAO propagates into the lower atmosphere and is the dynamical source or pacemaker for the large SC modulation of the QBO. The numerical results show that the upward propagating small-scale gravity waves from the troposphere amplify the SC modulations of the QBO and EAO in the stratosphere, part of the SC mechanism. The zonal winds of the equatorial QBO and EAO produce through the meridional circulation measurable SC variations in the temperature of the stratosphere and troposphere at high latitudes. Analysis of NCEP temperature and zonal wind data (1958 to 2006) provides observational evidence of the EAO with SC variations around 11 years.
文摘Effective calcium(Ca)management is crucial for optimizing oil palm cultivation and enhancing crop yield.This study aimed to gain insights into the dynamics of Ca concentration,accumulation,exportation,immobilization,and recycling in various oil palm organs relative to plant age.The experiment was conducted at the Agropalma enterprise site in the northeastern region of Para State,Brazil,evaluating seven plant age treatments:2,3,4,5,6,7,and 8 years old.Employing a completely randomized design with four replications.The results demonstrated an age-related increase in Ca concentration in petioles,rachis,arrows,male inflorescences,peduncles,and fruits.Furthermore,Ca accumulation exhibited an upward trend in all organs with progressing plant age.Notably,the study revealed an enhanced Ca use efficiency across all plant organs in correlation with the age of oil palm cultivation.These findings underscore the dynamic nutritional demands of oil palm,influencing Ca immobilization,cycling,and export throughout its developmental stages.
文摘The influence of hydrogen embrittlement on the fatigue behaviors of AISI 304 stainless steel is investigated. The fatigue endurance limits of the untreated and hydrogen-embrittled materials were almost the same at 400 MPa, and hydrogen embrittlement had little influence even though the sample contained about 8.1 times more hydrogen. Thus, the sensitivity of hydrogen gas in this material is very low. A surface crack initiation, growth, coalescence, and micro ridge model is proposed in this study. Slip line formation?⇒microcrack formation?⇒increases in the crack width, and blunting of the crack tip as it grows?⇒formation of many slip lines because of deformation in the shear direction?⇒growth of the crack in the shear direction, forming micro ridges, coalescence with adjacent cracks ⇒?continuous initiation, growth, coalescence, and ridge formation of surface cracks and specimen breakage.
