Predicting the next item that users may engage in is a key task of recommender systems, and many methods have been proposed to deal with this task from different aspects. Theoretically, the proper ...ensemble of multiple different methods (a.k.a. base models) can make more accurate and stable recommendations. However, most of the existing ensemble methods rely on static aggregation strategies, which fail to capture base models’ dynamic predictive abilities for each user over time. In addition, most of the existing diversity measures used in regression or classification ensemble methods rely on a distance metric of base models’ outputs, which makes it intractably apply for next-item recommendation whose base models output sequential ranking lists.
To solve the above problems, we propose a Sequential Ensemble Method, named SEM, to aggregate different base models for next-item recommendation. We assume users’ concentration and base models’ expertise can be inferred from users’ sequential behaviors and base models’ prediction results. Therefore, we propose to explicitly model base models’ dynamic predictive abilities on different users over time based on users’ concentration and base models’ expertise. In addition, we propose a new diversity measure for sequential ranking ensemble, which can perform diversity-based learning over time for better performance of next-item recommendation. Extensive experiments on six real-world data sets show that our method consistently outperforms state-of-the-art methods.
•Poper ensemble of multiple different methods can make more accurate and stable recommendations.•We explicitly model base models’ dynamic predictive abilities on different users over time for sequential ensemble learning.•We propose a new diversity measure that can perform diversity-based learning over time for better performance of the next-item recommendation.•Extensive experiments on six real-world data sets show that our method consistently outperforms state-of-the-art methods.
•Film cooling of a gel-fueled scramjet engine using incoming air is proposed.•The incoming air from the scramjet inlet is successfully compressed into the combustor.•Introducing the cooling strategy ...does not affect the scramjet inlet performance.•The temperature of the combustor walls can be effectively reduced.•Interaction mechanisms between the cooling flow and the mainstream are clarified.
Gel-fuels with metal particles have high specific impulse, lowered volatility and reduced risk of leakage compared with conventional liquid fuels, which are promising fuel candidates in scramjet engines. However, these non-Newtonian fluids with unique rheological properties are not suitable for active cooling. To address this issue, this paper proposes a film cooling strategy using the incoming air from the scramjet inlet, without introducing extra coolant tanks. Design of the coolant transport channel and the cooling slot is conducted; and the corresponding feasibility and cooling performance are evaluated within the flight Mach number range of 5.6–7.4 by validated numerical models. The numerical results reveal that the incoming air is successfully compressed into the combustor; in addition, the introduction of the film cooling has negligible effects on the mass flow coefficient, total pressure recovery coefficient and the compression ratio of the scramjet inlet. The sharp corners of the coolant inlet induce a system of shock waves and expansion waves, which lower the static and total pressure near the fuel injector by 2.5 % and 7 %, respectively. Such a fact implies limited effects on the combustion performance. Due to the high backpressure in the combustor, a normal shock wave forms in each coolant channel, which helps to further compress the coolant. Within 0–10 mm downstream the cooling slot, the film cooling effectiveness is above 0.5, which implies evidently reduced combustor wall temperature. The interaction and heat transfer mechanisms between the mainstream and the coolant flow are also explored based on the pressure field, flow field and the temperature field. These mechanisms are beneficial to optimize further the present cooling strategy.
The lithium–sulfur battery (Li–S battery) has attracted extensive attention because of its high energy density, but a series of disadvantages caused by sulfur insulation and the shuttle effect hinder ...the large-scale application of the Li–S battery. The conductive skeleton with strong adsorption on lithium polysulfide can effectively build the electron transmission path and inhibit the shuttle effect. In this study, a new type of chlorella-based biomass carbon skeleton carrying TiO2 metal sites (TiO2@CBBC) is designed and synthesized, and it was used as a functional separator modification material for the lithium sulfur battery. The biomass carbon skeleton has a unique three-dimensional skeleton and a unique specific surface, which can carry uniform titanium active sites and rich oxygen negative ions, so as to build a functional network of electron conduction, adsorbing polysulfide intermediates and promoting the dynamics of the sulfur conversion reaction. The Li–S battery equipped with a functional TiO2@CBBC separator shows excellent rate performance and cycle performance. The initial capacity of the lithium sulfur battery is up to 1011 mAh g–1 at 2C and can maintain 92% of the specific capacity after 100 cycles. At a stricter rate of 3C, the battery can still operate stably, and the coulomb efficiency remains above 95% throughout the entire process. This work represents a promising approach for developing the stability of lithium–sulfur batteries at a high rate.
Based on the mathematical analysis of the stable manifolds, unstable manifolds and solutions of subsystems, this paper provides methodologies to ensure the existence of homoclinic orbits (degenerate ...and non-degenerate) which cross the switching manifold transversally at two points in n-dimensional two-zone piecewise affine systems. In addition, two examples are provided to illustrate the effectiveness of the methods, moreover, the simulation results of homoclinic orbits and chaotic invariant sets are provided for the two examples.
Secretory proteins are cotranslationally or posttranslationally translocated across lipid membranes via a protein-conducting channel named SecY in prokaryotes and Sec61 in eukaryotes. The vast ...majority of secretory proteins in bacteria are driven through the channel posttranslationally by SecA, a highly conserved ATPase. How a polypeptide chain is moved by SecA through the SecY channel is poorly understood. Here, we report electron cryomicroscopy structures of the active SecA-SecY translocon with a polypeptide substrate. The substrate is captured in different translocation states when clamped by SecA with different nucleotides. Upon binding of an ATP analog, SecA undergoes global conformational changes to push the polypeptide substrate toward the channel in a way similar to how the RecA-like helicases translocate their nucleic acid substrates. The movements of the polypeptide substrates in the SecA-SecY translocon share a similar structural basis to those in the ribosome-SecY complex during cotranslational translocation.
Objective
To explore the association of geriatric nutrition risk index (GNRI), a traditional albumin-body weight calculation, with myopenia in patients with rheumatoid arthritis (RA) and compare its ...ability to identify myopenia with protein indicators.
Methods
This cross-sectional study was carried out based on a Chinese RA cohort. Clinical data and protein indicators (including albumin, globulin, albumin to globulin ratio, prealbumin, hemoglobin) were collected. GNRI was estimated by serum albumin and body weight. Myopenia was indicated as muscle mass loss measured by bioelectric impedance analysis.
Results
There were 789 RA patients included with mean age 52.6 ± 12.6 years and 77.6% female. There were 41.3%, 18.0%, 27.5%, 13.2% patients with no (GNRI > 98), low (GNRI 92 to ≤ 98), moderate (GNRI 82 to < 92), and major nutrition-related risk (GNRI < 82). There were 406 (51.5%) RA patients with myopenia, RA patients with major nutrition-related risk had the highest prevalence of myopenia (87.5%
vs.
73.3%
vs.
50.0%
vs.
26.1%). Multivariate logistic analysis showed that compared with no risk, RA patients with low (OR = 3.23, 95% CI: 1.86–5.61), moderate (OR = 9.56, 95% CI: 5.70–16.01), and major nutrition-related risk (OR = 28.91, 95% CI: 13.54–61.71) were associated with higher prevalence of myopenia. Receiver operating characteristic curves showed that GNRI (AUC = 0.79) performed a better identifiable ability toward myopenia than serum albumin (AUC = 0.66) or others indicators (AUC range 0.59 to 0.65), respectively.
Conclusion
GNRI, an objective and convenient albumin-weight index, may be preferable for identifying myopenia in RA patients.
Key Points
• We firstly elucidated the association of GNRI with muscle mass loss among RA patients, and compared its ability to identify muscle mass loss with serum albumin or other protein indicators.
• Major nutrition-related risk identified by GNRI showed the highest risk of muscle mass loss, GNRI demonstrated a greater ability to identify myopenia in RA patients. which indicated GNRI was an objective and convenient albumin-weight index to identify myopenia in RA patients.
Li- and Mn-rich layered oxide (LMR) materials are a promising candidates for next-generation Li-ion battery (LIB) anode materials because of their high specific capacity. However, their low initial ...Coulombic efficiency, voltage decay, and irreversible phase transition during cycling are the fatal drawbacks of LMR materials. This work reports on a cobalt-free LMR material composed of primary particles with a boron-induced exposed long- strip-like {010} plane. Because of this unique structure, the long strip-like cathode exhibits excellent electrochemical performance with a discharge capacity of 202 mAh g–1 at 1 C and a retention rate of 95.2% after 200 cycles. In addition, it is found that this long strip-like structure can modulate the redox of oxygen and enhance the reversibility. The irreversible phase transition process from the layered to a spinel and then to a rock-salt phase during cycling is also significantly suppressed. This work provides a feasible method for regulating the exposed {010} plane and a new idea for the structural design of LMR materials.
In recent years, naturally occurring tetrahydro-β-carboline (THC) alkaloids and their derivatives have been of biological interest. However, few studies and developments have reported the use of such ...structures in managing plant bacterial diseases. Herein, an array of novel THC derivatives containing an attractive 1,3-diaminopropan-2-ol pattern were prepared to evaluate the antiphytopathogen activity in vitro and in vivo and explore innovative antibacterial frameworks. Notably, target compounds exhibited excellent activities against three rebellious phytopathogens, namely, Pseudomonas syringae pv. actinidiae (Psa), Xanthomonas axonopodis pv. citri, and Xanthomonas oryzae pv. oryzae, at related optimal EC50 values of 2.39 (II 9 ), 2.06 (I 23 ), and 1.69 (II 9 ) μg/mL, respectively. These effects were superior to those of the parent structure 1,2,3,4-THC and positive controls. In vivo assays showed that II 9 exhibited excellent control efficiencies of 51.89 and 65.45% at 200 μg/mL against rice bacterial blight and kiwifruit bacterial canker, respectively, and I 23 substantially relieved the citrus canker on the leaves. Antibacterial mechanisms indicated that these THC compounds could induce the increment of reactive oxygen species and subsequently endow the tested bacteria with distinct apoptotic behavior. In addition, II 9 could alleviate the hypersensitive response and pathogenicity of Psa. Overall, these simple THC derivatives can be further developed as versatile antibacterial agents.
The computed tomography (CT) features of hepatic veno-occlusive disease (HVOD) could play a role in its diagnosis. We aimed to perform a meta-analysis of studies examining the CT features of HVOD.
...Relevant studies published up to May 3, 2017 were searched in major electronic databases. The extracted data included the proportion of various CT features in patients with HVOD. The meta-analysis was conducted using R 3.3.3 with the "meta" package.
Eleven studies were included. The studies involved 326 patients with a mean age range of 50.2-58.9 years, and the proportion of female patients ranged from 20% to 57.5%. The meta-analysis showed the pooled proportion of CT features: hepatic parenchyma with heterogeneous hypoattenuation (81.05%, 95% confidence interval CI: 56.97%-93.25%), patchy enhancement in the portal venous phase (87.09%, 95% CI: 75.15%-93.77%) with or without a narrow or invisible hepatic vein (71.02% 95% CI: 42.09%-89.20%), gallbladder wall edema (65.51%, 95% CI: 28.98%-89.84%), and patchy heterogeneous enhancement in the arterial phase (44.36%, 95% CI: 29.98%-59.76%) with or without slightly enlarged hepatic artery (56.61%, 95% CI: 40.62%-71.33%).
Hepatic parenchyma with heterogeneous hypoattenuation and patchy enhancement with or without narrowing or an invisible hepatic vein in the portal venous or equilibrium phase may be the most important CT feature for diagnosing HVOD.
