•Deformed steel fibers in UHPC provide better pullout resistance than straight steel fiber.•Highest average bond strengths of straight and deformed steel fibers in UHPC are obtained at inclination ...angle of 30° or 45°.•Highest pullout energies are obtained in twisted and half-hooked steel fibers at aligned and highly inclined conditions, respectively.•Best tensile performance of UHPFRC is found with straight steel fiber, followed by twisted, half-hooked, and hooked steel fibers.•Correlation between single fiber pullout and tensile behaviors of UHPFRC with deformed steel fibers is fairly low.
This study investigates the effects of steel fiber type on the pullout and tensile performance of ultra-high-performance fiber-reinforced concrete (UHPFRC). For this, four different types of steel fibers, i.e., straight, twisted, hooked, and half-hooked, were used. In order to consider random fiber orientation in UHPFRC, various inclination angles, ranging from 0° to 60°, were considered for the pullout tests. Test results indicated that better pullout resistance was obtained in the deformed (twisted, hooked, and half-hooked) steel fibers embedded in ultra-high-performance concrete (UHPC) than that of the straight steel fiber as fiber breakage was prevented. The highest bond strengths of all steel fiber types were found when they were inclined 30° or 45°, while their slip capacities increased with increasing inclination angle. The hooked steel fiber exhibited the highest bond strengths at all inclination angles, while the twisted and half-hooked steel fibers exhibited the highest pullout energies at aligned and highly inclined (45° and 60°) conditions, respectively. In contrast to the pullout test results, the best tensile performance of UHPFRC was achieved by incorporating straight steel fibers, followed by the twisted, half-hooked, and hooked steel fibers. The poorer tensile performance of UHPCs reinforced with the deformed steel fibers was because of the severe matrix damage from excessive mechanical anchorage and fiber congestion, leading to insufficient matrix volume. Similarly, a relatively weak correlation between the fiber pullout and tensile behaviors of UHPFRC was observed. Therefore, a new pullout test method, which is able to consider the fiber random orientation and spacing, is required in order to improve the correlation.
Shedding light on disordered proteins
Disordered proteins often fold as they bind to a partner protein. There could be many different molecular trajectories between the unbound proteins and the bound ...complex. Most methods to measure transition paths rely on monitoring a single distance, making it difficult to resolve complex pathways. Kim and Chung used fast three-color single-molecule Foster resonance energy transfer (FRET) to simultaneously probe distance changes between the two ends of an unfolded protein and between each end and a probe on the partner protein. They show that binding can be initiated by diverse conformations and that the molecules are held together by non-native interactions as the disordered protein folds. This allows the association to be diffusion limited because most collisions lead to binding.
Science
, this issue p.
1253
Three-color single-molecule Förster resonance energy transfer reveals diverse binding transition paths of disordered proteins.
Transition paths of macromolecular conformational changes such as protein folding are predicted to be heterogeneous. However, experimental characterization of the diversity of transition paths is extremely challenging because it requires measuring more than one distance during individual transitions. In this work, we used fast three-color single-molecule Förster resonance energy transfer spectroscopy to obtain the distribution of binding transition paths of a disordered protein. About half of the transitions follow a path involving strong non-native electrostatic interactions, resulting in a transition time of 300 to 800 microseconds. The remaining half follow more diverse paths characterized by weaker electrostatic interactions and more than 10 times shorter transition path times. The chain flexibility and non-native interactions make diverse binding pathways possible, allowing disordered proteins to bind faster than folded proteins.
This study examines the implications of the fiber type and the distance between fibers on the pullout behavior of steel fibers embedded in ultra-high-performance concrete (UHPC). For this, three ...different types of steel fibers, i.e., straight, hooked, and twisted, and four different distances between fibers, corresponding to fiber volume fractions of 1%, 2%, and 7% and a fiber bundle, were considered. To evaluate the effect of the distance between fibers, four individual fibers were included in a single dog-bone specimen, and a single fiber specimen was also fabricated and tested as a control specimen. Test results indicate that the twisted steel fiber exhibited the greatest pullout resistance, followed by the hooked and straight steel fibers. Approximately 30% lower bond strengths were obtained for the specimens with multiple fibers as compared to those with a single fiber, regardless of the fiber type and distance between fibers. The average bond strengths of the hooked and twisted steel fibers were improved by decreasing the distance between fibers up to 1 mm, corresponding to a volume fraction of 7%, while the bundled fiber specimens provided the poorest pullout resistance in terms of bond strength and energy absorption capacity for all types of fibers. The reduction rate of pullout resistance was the most significant for the straight fiber, relative to the hooked and twisted fibers. Minor matrix damage was obtained for the straight fiber specimen, and its pullout performance was not influenced by the surrounding fibers. In contrast, severe matrix damage was observed for the hooked and twisted fibers, and they were overlapped, causing a larger spalling area with a closer fiber distance.
This study examined the electrical and self-sensing capacities of ultra-high-performance fiber-reinforced concrete (UHPFRC) with and without carbon nanotubes (CNTs). For this, the effects of steel ...fiber content, orientation, and pore water content on the electrical and piezoresistive properties of UHPFRC without CNTs were first evaluated. Then, the effect of CNT content on the self-sensing capacities of UHPFRC under compression and flexure was investigated. Test results indicated that higher steel fiber content, better fiber orientation, and higher amount of pore water led to higher electrical conductivity of UHPFRC. The effects of fiber orientation and drying condition on the electrical conductivity became minor as sufficiently high amount of steel fibers, 3% by volume, was added. Including only steel fibers did not impart UHPFRC with piezoresistive properties. Addition of CNTs substantially improved the electrical conductivity of UHPFRC. Under compression, UHPFRC with a CNT content of 0.3% or greater had a self-sensing ability that was activated by the formation of cracks, and better sensing capacity was achieved by including greater amount of CNTs. Furthermore, the pre-peak flexural behavior of UHPFRC was precisely simulated with a fractional change in resistivity when 0.3% CNTs were incorporated. The pre-cracking self-sensing capacity of UHPFRC with CNTs was more effective under tensile stress state than under compressive stress state.
We aimed to develop a novel prediction model for early neurological deterioration (END) based on an interpretable machine learning (ML) algorithm for atrial fibrillation (AF)-related stroke and to ...evaluate the prediction accuracy and feature importance of ML models. Data from multicenter prospective stroke registries in South Korea were collected. After stepwise data preprocessing, we utilized logistic regression, support vector machine, extreme gradient boosting, light gradient boosting machine (LightGBM), and multilayer perceptron models. We used the Shapley additive explanation (SHAP) method to evaluate feature importance. Of the 3,213 stroke patients, the 2,363 who had arrived at the hospital within 24 h of symptom onset and had available information regarding END were included. Of these, 318 (13.5%) had END. The LightGBM model showed the highest area under the receiver operating characteristic curve (0.772; 95% confidence interval, 0.715-0.829). The feature importance analysis revealed that fasting glucose level and the National Institute of Health Stroke Scale score were the most influential factors. Among ML algorithms, the LightGBM model was particularly useful for predicting END, as it revealed new and diverse predictors. Additionally, the effects of the features on the predictive power of the model were individualized using the SHAP method.
Intrinsically disordered proteins (IDPs) usually fold during binding to target proteins. In contrast to interactions between folded proteins, this additional folding step makes the binding process ...more complex. Understanding the mechanism of coupled binding and folding of IDPs requires analysis of binding pathways that involve formation of the transient complex (TC). However, experimental characterization of TC is challenging because it only appears for a very brief period during binding. Here, we use single-molecule fluorescence spectroscopy to investigate the mechanism of diffusion-limited association of an IDP. A large enhancement of the association rate is observed due to the stabilization of TC by non-native electrostatic interactions. Moreover, photon-by-photon analysis reveals that the lifetime of TC for IDP binding is at least two orders of magnitude longer than that for binding of two folded proteins. This result suggests the long lifetime of TC is generally required for folding of IDPs during binding processes.
This study investigates the effects of matrix shrinkage, fiber geometry, and loading rate on the pullout behavior of steel fibers embedded in ultra-high-performance concrete (UHPC). For varying the ...matrix shrinkage, different quantities of calcium sulfoaluminate-based (CSA) expansive agent (EA) were adopted, ranging from 0% to 8%. In addition, moderately and highly deformed, i.e., half-hooked (HH) and twisted (T), steel fibers were used along with three different loading rates ranging from 0.018 (static) to 793 mm/s (impact). The test results indicated that the addition of the CSA EA is effective in reducing the shrinkage strains of UHPC only when its quantity is greater than 6%. The addition of the CSA EA improved the static average bond strengths of all the HH- and T-fibers; however, its effectiveness on the pullout energy was only valid when these fibers were aligned. The addition of the CSA EA enhanced the dynamic bond strengths of HH- and T-fibers, and the improvement was more obvious in the T-fiber specimens than in the HH-fiber specimens and in the aligned fibers than in the inclined ones. However, its implication on the dynamic pullout energies of the HH- and T-fibers was ambiguous. Both the addition of the CSA EA and a faster loading rate increased the probability of rupture failure of the deformed steel fibers in UHPC. The loading rate sensitivity was the highest in the straight steel fiber in UHPC, followed by the HH- and T-fibers, respectively. Consequently, straight or moderately deformed steel fibers are recommended for use in reinforcing UHPC under extreme loads, such as impact and blast.
Handgrip strength (HGS) is acknowledged as a key indicator of overall physical fitness and is associated with various health outcomes.
This research investigates the correlation between HGS and ...quality of life (QoL), focusing on its relation to pulmonary function in the general adult population.
The study involved 19,402 participants aged 40 and above, spanning from 2014 to 2019, who underwent pulmonary function and HGS tests. Participants were categorized based on lung function, and regression analyses were employed to examine the relationship between HGS and QoL, with adjustments made for lung function.
The average age of the cohort was 58.2 years, comprising 44.6% males and 41.2% smokers. Out of the 18,708 participants who completed the European Quality of Life Scale-Five Dimensions (EQ-5D-3L) assessment, higher severity levels in mobility, self-care, usual activities, pain or discomfort, and anxiety or depression were linked to lower HGS in both sexes. Additionally, among the 3,723 participants who completed the Health-related Quality of Life Instrument with 8 Items (HINT-8) assessment, higher severity levels in pain, work, and depression were associated with lower HGS in men. In women, higher severity levels in climbing stairs, pain, vitality, and work correlated with lower HGS.
As problems indicated by EQ-5D worsened, there was a consistent decrease in handgrip strength (HGS) across both genders. The HINT-8 assessment further revealed that increased severity in pain and work-related issues led to reduced HGS in both men and women. This study highlights the relationship between HGS and Quality of Life (QoL), taking lung function into consideration, and underscores the importance of HGS as a potential marker of physical health and fitness.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
This study examines the effectiveness of using curvilinear steel fibers to enhance the pullout resistance of conventional straight steel (S-) fiber for an ultra-high-performance concrete (UHPC) ...matrix. Because structures composed of UHPC are subjected to various loading conditions and have random fiber orientations, three different loading rates ranging from static (0.018 mm/s) to impact (up to 906.2 mm/s) and two inclination angles of 0° and 45° were adopted. To fabricate the novel curvilinear steel fibers, five different curvatures were also utilized. Test results indicated that the curvilinear fibers provided a clearly higher pullout resistance than that of the conventional S-fiber, and the effectiveness increased with the curvature, regardless of the inclination angle and loading rate. Higher bond strengths were obtained for the S- and curvilinear fibers when they were inclined at 45° rather than aligned. In general, the bond strengths and pullout energies of the S- and curvilinear fibers in UHPC were improved by increasing the loading rate, and a higher loading rate sensitivity on the bond strengths was observed in aligned fibers than in inclined fibers. The matrix spalling phenomenon was only observed in an inclined state and became more significant with an increasing curvature and loading rate. The developed curvilinear fibers provided noticeably smaller matrix spalling areas than the conventional deformed steel fibers under both static and impact conditions, owing to the mitigated stress concentration. Thus, these may be worthy of attention as a novel reinforcing fiber type for UHPC composites.
To use a calcium sulfoaluminate (CSA) expansive agent (EA), beneficial for volume stability of concrete, its effect on the pullout behavior of straight steel fiber in ultra-high-performance concrete ...(UHPC) needs to be analyzed under various loads, from static to impact (0.018 to 1244 mm/s). Adding CSA EA enhanced the static pullout resistance of only inclined fibers, whereas the average bond strengths and pullout energies of both the aligned and inclined fibers improved by it under impact loading. Thus, adding the CSA EA is more effective in enhancing the dynamic pullout resistance. The fiber pullout resistance improved at a higher loading rate, and 45°-inclination of the fibers improved the dynamic pullout resistance. A higher rate sensitivity on the bond strength was observed with the CSA EA addition and fiber's inclination, and the pullout energy was more dependent on loading rate than the average bond strength as fiber rupture was prevented.
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