•The effects of compositions on freeze–thaw resistance of UHPC were studied.•The SEM and MIP tests were conducted to reveal the freeze–thaw mechanism of UHPC.•The grey correlation entropy was used to ...evaluate the influence extent of factors on the freeze–thaw resistance of UHPC.
The concrete compositions have a crucial influence on the freeze–thaw resistance of ultra-high performance concrete (UHPC). The UHPCs with different concrete compositions were designed and prepared. Based on weight measurement and compressive strength test, the mass loss rate and compressive strength loss rate were used to evaluate the influence of different factors (water binder ratio, steel fiber, superplasticizer, silica fume and fly ash) on the freeze–thaw resistance of UHPC. The scanning electron microscope (SEM) test and mercury intrusion porosimetry (MIP) test were carried out to reveal the freeze–thaw mechanism of UHPC. Furthermore, the grey correlation entropy method was employed to evaluate the influence extent of different factors on the freeze–thaw resistance of UHPC. The results show that the freeze–thaw resistance of UHPC can be improved with the reduction of water binder ratio, which indicates the lower average pore size and cumulative pore volume of UHPC with lower water binder ratio. The steel fiber, silica fume and fly ash can improve the freeze–thaw resistance of UHPC at a proper content. Among these factors, the most significant influencing factor is the water binder ratio, followed by the silica fume, steel fiber, superplasticizer, and the fly ash shows the least effect on the freeze–thaw resistance of UHPC.
SUMMARY
The Salton Sea Geothermal Field (SSGF) is one of the most seismically active and geothermally productive fields in California. Here we present a detailed analysis of short-term seismicity ...change in SSGF from 2008 to 2013 during and right following large distant earthquakes, as well as long-term seismicity change due to geothermal productions. We first apply a GPU-based waveform matched-filter technique (WMFT) to the continuous data recorded by the Calenergy Borehole (EN) Network and detect more than 70 000 new micro-earthquakes than listed in the standard Southern California Seismic Network catalogue. We then analyse the seismicity rate changes in the SSGF associated with transient stress fluctuations triggered by regional and large teleseismic earthquakes from 1999 to 2019. We find triggered seismicity in the SSGF following seven regional M > 5.5 earthquakes. In comparison, most teleseismic earthquakes with M > 8.0 did not trigger significant seismicity rate change in the SSGF, likely indicating a frequency dependence in remote dynamic triggering. We further characterize the correlation between the long-term seismicity rate and geothermal production rates, and the temporal and spatial distribution of Guttenberg–Richter b-values inside and outside the SSGF with the newly detected catalogue. The long-term seismicity shows that events with M > 1.5 are likely correlated with net production rates, while smaller events do not show any correlation. The b-values inside the SSGF are higher than those outside the SSGF, and the locations of dynamically triggered events are close to locations with high b-values.
In an effort to address the problem of hypersonic morphing vehicles reaching the target while avoiding no-fly zones, an improved predictor–corrector guidance method is proposed. Firstly, the aircraft ...motion model and the constraint model are established. Then, the basic algorithm is given. The Q-learning method is used to design the attack angle and sweep angle scheme to ensure that the aircraft can fly over low-altitude zones. The B-spline curve is used to determine the locations of flight path points, and the bank angle scheme is designed using the predictor–corrector method, so that the aircraft can avoid high-altitude zones. Next, the Monte Carlo reinforcement learning (MCRL) method is used to improve the predictor–corrector method and a Deep Neural Network (DNN) is used to fit the reward function. The planning method in this paper realizes the use of a variable sweep angle, while the improved method further improves the performance of the trajectory, including the attainment of greater final speed and a smaller turning angle. The simulation results verify the effectiveness of the proposed algorithm.
Stress proteins located in the cytosol or endoplasmic reticulum (ER) maintain cell homeostasis and afford tolerance to severe insults. In neurodegenerative diseases, several chaperones ameliorate the ...accumulation of misfolded proteins triggered by oxidative or nitrosative stress, or of mutated gene products. Although severe ER stress can induce apoptosis, the ER withstands relatively mild insults through the expression of stress proteins or chaperones such as glucose-regulated protein (GRP) and protein-disulphide isomerase (PDI), which assist in the maturation and transport of unfolded secretory proteins. PDI catalyses thiol–disulphide exchange, thus facilitating disulphide bond formation and rearrangement reactions. PDI has two domains that function as independent active sites with homology to the small, redox-active protein thioredoxin. During neurodegenerative disorders and cerebral ischaemia, the accumulation of immature and denatured proteins results in ER dysfunction, but the upregulation of PDI represents an adaptive response to protect neuronal cells. Here we show, in brains manifesting sporadic Parkinson's or Alzheimer's disease, that PDI is S-nitrosylated, a reaction transferring a nitric oxide (NO) group to a critical cysteine thiol to affect protein function. NO-induced S-nitrosylation of PDI inhibits its enzymatic activity, leads to the accumulation of polyubiquitinated proteins, and activates the unfolded protein response. S-Nitrosylation also abrogates PDI-mediated attenuation of neuronal cell death triggered by ER stress, misfolded proteins or proteasome inhibition. Thus, PDI prevents neurotoxicity associated with ER stress and protein misfolding, but NO blocks this protective effect in neurodegenerative disorders through the S-nitrosylation of PDI.
Large earthquakes are capable of triggering either shallow earthquakes or deep tectonic tremors at long‐range distances. So far, most of remotely triggered tremors were found along major plate ...boundary faults around the Pacific Rim. Here we conduct a systematic search for remotely triggered earthquakes and tremors in South/Southeast Asia following the 11 April 2012 Mw 8.6 Indian Ocean earthquake. We find additional evidence of triggered tectonic tremors beneath the Java Island and the Sulabes Island in Eastern Indonesia and triggered earthquakes in Vietnam. Tremors mostly occurred during the large‐amplitude Rayleigh waves of the Indian Ocean main shock and were also triggered by several other large distant earthquakes. Although we are unable to locate them, they were recorded at stations close to major tectonic faults, suggesting that they are likely of tectonic origin. However, we find no evidence of triggered tremor/earthquakes along the Sumatra subduction zone and eastern portion of Himalaya frontal thrusts, indicating that remote triggering was not as widespread as previously thought.
Key Points
We find three new sites of remotely triggered activity in South/Southeast Asia following the 2012 Indian Ocean earthquake
Triggered tremors/earthquakes mostly occurred during the large‐amplitude Rayleigh waves and were close to active faults
We did not find any clear evidence of remotely triggered seismicity along the Sumatra subduction zone and northeastern Himalaya frontal thrusts
Huntington's disease is caused by an expanded CAG repeat in the gene encoding huntingtin (HTT), resulting in loss of striatal and cortical neurons. Given that the gene product is widely expressed, it ...remains unclear why neurons are selectively targeted. Here we show the relationship between synaptic and extrasynaptic activity, inclusion formation of mutant huntingtin protein (mtHtt) and neuronal survival. Synaptic N-methyl-D-aspartate-type glutamate receptor (NMDAR) activity induces mtHtt inclusions via a T complex-1 (TCP-1) ring complex (TRiC)-dependent mechanism, rendering neurons more resistant to mtHtt-mediated cell death. In contrast, stimulation of extrasynaptic NMDARs increases the vulnerability of mtHtt-containing neurons to cell death by impairing the neuroprotective cyclic AMP response element-binding protein (CREB)-peroxisome proliferator-activated receptor-gamma coactivator-1alpha (PGC-1alpha) cascade and increasing the level of the small guanine nucleotide-binding protein Rhes, which is known to sumoylate and disaggregate mtHtt. Treatment of transgenic mice expressing a yeast artificial chromosome containing 128 CAG repeats (YAC128) with low-dose memantine blocks extrasynaptic (but not synaptic) NMDARs and ameliorates neuropathological and behavioral manifestations. By contrast, high-dose memantine, which blocks both extrasynaptic and synaptic NMDAR activity, decreases neuronal inclusions and worsens these outcomes. Our findings offer a rational therapeutic approach for protecting susceptible neurons in Huntington's disease.
Due to the enclosed environment of greenhouse grape production, the supply of CO 2 required for photosynthesis is often insufficient, leading to photosynthetic downregulation and reduced yield. ...Currently, the optimal CO 2 concentration for grape production in greenhouses is unknown, and the precise control of actual CO 2 levels remains a challenge. This study aims to investigate the effects of different CO 2 concentrations on the photosynthetic characteristics and yield of grapes, to validate the feasibility of a CO 2 gas irrigation system, and to identify the optimal CO 2 concentration for greenhouse grape production. In this study, a CO 2 gas irrigation system combining CO 2 enrichment and gas irrigation techniques was used with a 5-year-old Eurasian grape variety ( Vitis vinifera L.) ‘Flame Seedless.’ Four CO 2 concentration treatments were applied: 500 ppm (500 ± 30 µmol·mol −1 ), 700 ppm (700 ± 30 µmol·mol −1 ), 850 ppm (850 ± 30 µmol·mol −1 ), and 1,000 ppm (1,000 ± 30 µmol·mol −1 ). As CO 2 concentration increased, chlorophyll a, chlorophyll b, and carotenoids in grape leaves all reached maximum values at 700 ppm and 850 ppm during the same irrigation cycle, while the chlorophyll a/b ratio was lower than at other concentrations. The net photosynthetic rate (Pn) and water use efficiency (WUE) of grape leaves were the highest at 700 ppm. The transpiration rate and stomatal conductance at 700 ppm and 850 ppm were significantly lower than those at other concentrations. The light saturation point and apparent quantum efficiency reached their maximum at 850 ppm, followed by 700 ppm. Additionally, the maximum net photosynthetic rate, carboxylation efficiency, electron transport rate, and activities of SOD, CAT, POD, PPO, and RuBisCO at 700 ppm were significantly higher than at other concentrations, with the highest yield recorded at 14.54 t·hm −2 . However, when the CO 2 concentration reached 1,000 ppm, both photosynthesis and yield declined to varying degrees. Under the experimental conditions, the optimal CO 2 concentration for greenhouse grape production was 700 ppm, with excessive CO 2 levels gradually inhibiting photosynthesis and yield. The results provide a theoretical basis for the future application of CO 2 fertilization and gas irrigation techniques in controlled greenhouse grape production.
We report a procedure to fabricate antibacterial core/shell polymer nanoobjects with sheetlike, cylindrical, and spherical shapes. These shaped nanoobjects with chemically cross-linked polysiloxane ...cores and densely grafted polyammoniums shells were prepared by dispersing cross-linked microphase-separated materials of diblock copolymers, poly(2-(dimethylamino)ethyl methacrylate)-block-poly(3-(triethoxysilyl)propyl methacrylate) (PDMAEMA-b-PTEPM). Shapes of the nanoobjects were controlled by block copolymer composition, namely the microphase-separated structures. Then the tethered PDMAEMA shells were further quaternized with n-octyl bromide. The diblock copolymers, microphase-separated materials and shaped nanoobjects before and after quaternization were studied by 1H NMR, size exclusion chromatography (SEC), small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM), and Fourier-transform infrared spectroscopy (FT-IR). The antibacterial activities of these quaternized nanoobjects have been preliminarily assessed against bacteria Escherichia coli (E. coli) (8099). The minimum bactericidal concentration (MBC) of the sheets, cylinders and spheres were 1.00, 0.66, 0.66 mg/mL. The antibacterial activities of the quaternized nanoobjects were nearly ten times higher than that of quaternized PDMAEMA homopolymer.
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Accumulation of aberrant proteins to form Lewy bodies (LBs) is a hallmark of Parkinson's disease (PD). Ubiquitination-mediated degradation of aberrant, misfolded proteins is critical for maintaining ...normal cell function. Emerging evidence suggests that oxidative/nitrosative stress compromises the precisely-regulated network of ubiquitination in PD, particularly affecting parkin E3 ligase activity, and contributes to the accumulation of toxic proteins and neuronal cell death.
To gain insight into the mechanism whereby cell stress alters parkin-mediated ubiquitination and LB formation, we investigated the effect of oxidative stress. We found significant increases in oxidation (sulfonation) and subsequent aggregation of parkin in SH-SY5Y cells exposed to the mitochondrial complex I inhibitor 1-methyl-4-phenlypyridinium (MPP+), representing an in vitro cell-based PD model. Exposure of these cells to direct oxidation via pathological doses of H2O2 induced a vicious cycle of increased followed by decreased parkin E3 ligase activity, similar to that previously reported following S-nitrosylation of parkin. Pre-incubation with catalase attenuated H2O2 accumulation, parkin sulfonation, and parkin aggregation. Mass spectrometry (MS) analysis revealed that H2O2 reacted with specific cysteine residues of parkin, resulting in sulfination/sulfonation in regions of the protein similar to those affected by parkin mutations in hereditary forms of PD. Immunohistochemistry or gel electrophoresis revealed an increase in aggregated parkin in rats and primates exposed to mitochondrial complex I inhibitors, as well as in postmortem human brain from patients with PD with LBs.
These findings show that oxidative stress alters parkin E3 ligase activity, leading to dysfunction of the ubiquitin-proteasome system and potentially contributing to LB formation.
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