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Submodular maximization is well studied in the fields of data mining and machine learning. We study the submodular maximization subject to a cardinality constraint k for large scale scenarios applications under two combined settings. One is that all elements arrive in a streaming fashion, and the other is that some elements may be invalid at last. For this problem, which is called streaming robust submodular maximization (SRSM) problem, we explore an approximation algorithm, returning a subset S from the ground set V with a limit size, such that it represents V and is robust to a broken set E well. Our algorithm only makes one pass over data, and achieves a constant-factor 0.1224 approximation guarantee, independent of the cardinality constraint parameter k. Based on the algorithm for SRSM problem, we continue to discuss this problem over sliding windows, in which we are asked to obtain a proper set that only considers the last W elements, and derive an algorithm with a constant (0. 0612 − ϵ) -approximation guarantee. At last we also propose numerical experiments on some applications to well demonstrate our algorithm for SRSM problem over sliding windows. [ABSTRACT FROM AUTHOR]

Herein, efficient fabrication of polymersomes that have unique and nonequilibrium morphologies is reported. Starting from preparing big polymeric vesicles sized around 2 µm with a flexible but crosslinkable structure, a controllable morphological transformation process from the vesicles via prolate vesicles and the pearl‐chain‐like structure, which are the two intermediate structures, to vesicle‐end‐capped tubes is conducted. Significantly, each of the intermediates is a regular polymersome and occupies a distinct phase space in the transformation process and thus can be separately processed and prepared. By crosslinking the structures, respectively, regular polymersomes with unique but stable morphologies are fabricated. Furthermore, the 1D polymersomes contain narrow necks. These narrow necks are sensitive to ultrasound vibration and broken by gentle ultrasound treatment to form regular open‐ended tubes and open‐ended vesicles, which are nonequilibrium but stable morphologies and difficult to prepare by existing methods. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the two-stage submodular maximization problem, where there is a collection F = { f 1 ,... , f m } of m submodular functions which are defined on the same element ground set Ω. The goal is to select a subset S ⊆ Ω of size at most ℓ such that 1 m ∑ f ∈ F max T ⊆ S , T ∈ I ⁡ f (T) is maximized, where I denotes a specifically-defined independence system. We consider the two-stage submodular maximization with a P -matroid constraint and present a (1 / (P + 1)) (1 − 1 / e (P + 1)) -approximation algorithm. Furthermore, we extend the algorithm to the two-stage submodular maximization with a more generalized P -exchange system constraint and show the approximation ratio can be maintained with slightly modifications of the algorithm. [ABSTRACT FROM AUTHOR]

In this paper, we study the problem of maximizing a sequence submodular function in the streaming setting, where the utility function is defined on sequences instead of sets of elements. We encode the sequence submodular maximization with a weighted digraph, in which the weight of a vertex reveals the utility value in selecting a single element and the weight of an edge reveals the additional profit with respect to a certain selection sequence. The edges are visited in a streaming fashion and the aim is to sieve a sequence of at most k elements from the stream, such that the utility is maximized. In this work, we present an edge-based threshold procedure, which makes one pass over the stream, attains an approximation ratio of (1 / (2 Δ + 1) - O (ϵ)) , consumes O (k Δ / ϵ) memory source in total and O (log (k Δ) / ϵ) update time per edge, where Δ is the minimum of the maximal outdegree and indegree of the directed graph. [ABSTRACT FROM AUTHOR]

Maximizing constrained submodular functions lies at the core of substantial machine learning and data mining. Specially, the case that the data come in a streaming fashion receives more attention in recent decades. In this work, we study the approximation algorithm for maximizing a non-decreasing set function under d-knapsack constraint. Based on the diminishing-return ratio for set functions, a non-trivial algorithm is devised for maximizing the set function without submodularity. Our results cover some known results and provide an effective method for the maximization on set functions no matter they are submodular or not. We also run the algorithm to handle the application of support selection for sparse linear regression. Numerical results show that the output quality of the algorithm is good. [ABSTRACT FROM AUTHOR]

The pioneering exfoliation of monolayer tungsten diselenide has greatly inspired researchers toward semiconducting applications. WSe2 belongs to a family of transition‐metal dichalcogenides. Similar to graphene, WSe2 and analogous dichalcogenides have layered structures with weak van der Waals interactions between two adjacent layers. First, the readers are presented with the fundamentals of WSe2, such as types, morphologies, and properties. Here, we report the characterization principles and practices such as microscopy, spectroscopy, and diffraction. Second, the methods for obtaining high‐quality WSe2, such as exfoliation, hydrothermal and chemical vapor deposition, are briefly listed. With advantages of light weight, flexibility, and high quantum efficiency, 2D materials may have a niche in optoelectronics as building blocks in p‐n junctions. Therefore, we introduce a state‐of‐the‐art demonstration of heterostructure devices employing the p‐type WSe2 semiconductor. The device architectures include field‐effect transistors, photodetectors, gas sensors, and photovoltaic solar cells. Due to its unique electronic, optical, and energy band properties, WSe2 has been increasingly investigated due to the conductivity of the p‐type charge carrier upon palladium contact. Eventually, the dynamic research on WSe2 and van der Waals heterostructures is summarized to arouse the passion of the 2D research community. [ABSTRACT FROM AUTHOR]

Active friending is a problem in social networks that is to assist a user to build a relationship to a target user by sending invitations to a set of intermediate users; the goal is to maximize the acceptance probability at the target node taking advantage of the social influence through the network formed by the intermediate nodes. In this paper, we convert the original formulated active friending problem of nonsubmodular maximization subject to cardinality constraint into a submodular cost submodular knapsack problem in the IC model, and we show that the two problems are equivalent. We similarly make the conversion on the active friending in the LT model. Then we give a general combinatorial optimization algorithm to solve active friending problems in both the IC model and the LT model with a guaranteed approximation. We analyze the computational complexity of the problem and the algorithm performance. The effectiveness of the generalized method is verified on real data sets. [ABSTRACT FROM AUTHOR]

A Gram-staining-positive and aerobic coccus with the ability to degrade petroleum bacterium, designated Y42T, was isolated from the Lenghu oil field located in the northern margin of the Qaidam Basin. Phylogenetic and signature nucleotides analyses revealed that strain Y42T belongs to the genus Planococcus. The multiple sequence alignments of 16S rRNA and housekeeping genes showed that strain Y42T formed a distinct lineage with the other Planococcus clade. The average nucleotide identity (ANI) and DNA–DNA hybridization values (DDH) between strain Y42T and the reference strains were 69.5–70.1 and 19.4–21.7%, respectively, which values were below the threshold for species delineation. The major fatty acids of strain Y42T were anteiso-C15:0. The respiratory quinone was MK-7 (71.8%) as the predominant menaquinone followed the MK-6 (28.2%) and the cell-wall hydrolysates contained LL-diaminopimelic acid. The polar lipid was composed of diphosphatidyl glycerol, phosphatidyl glycerol, phosphoglycolipid, aminophospholipid and four unidentified lipids. The peptidoglycan type was A4α (l-Lys–d-Glu). The strain Y42T possessed larger genome (approximately 4 MB) and revealed obvious differences for the abundance of the COG categories compared with the other Planococcus bacteria. Also, the strain Y42T also possessed more unique orthologous proteins. The structural characteristics of the strain Y42T genome provided a competitive advantage for better survival in petroleum-polluted environments. Combined with the 16S rRNA gene and genome sequence, phenotypic as well as chemotaxonomic characterisations, strain Y42T is considered to represent a novel species of the genus Planococcus, for which the name Planococcus lenghuensis sp. nov. be proposed. The type strain is Y42T (= CGMCC 1.15921T = JCM 32719T). [ABSTRACT FROM AUTHOR]

Metal halide perovskite nanocrystals are sought after for many optical and optoelectronic applications, such as light‐emitting diode and solar cells, due to their outstanding optical properties. However, their ionic nature makes them susceptible to ambient conditions. One rational solution to this challenge is the passivation or encapsulation of perovskite nanocrystals to isolate them from their environments. Thus, there is an urgent need to develop efficient methods for encapsulating emissive perovskite nanocrystals. A facile post‐synthesis method is proposed to treat CsxFA(1−x)PbBr3 nanocrystals, in the presence of Fe3+ cations, to create a robust and water‐stable nanocomposite structure, where 3D CsPbBr3 nanocrystals are embedded in and thus protected by the 2D CsPb2Br5 nanosheets (named as CsPbBr3/CsPb2Br5 hereafter). These Fe3+ cations facilitate the formation of the CsPbBr3/CsPb2Br5 composite and regulate the growth of 2D CsPb2Br5 sheets. By performing controlled experiments, the possible mechanism of 2D nanosheet growth is proposed and discussed in detail. More importantly, the composite can remain stable in water for three months and exhibits amplified spontaneous emission under femtosecond laser irradiation. This work presents a synthesis pathway for producing durable perovskite composites that are promising for future lasing applications. [ABSTRACT FROM AUTHOR]

• A Sn 3 O 4 nanosheet/Ni foam photoelectrocatalyst was synthesized with efficiency degradation rate for the polyacrylamide. • The Sn 3 O 4 nanosheet/Ni foam heterostructure can extend the absorption range to 725 nm. • The Sn 3 O 4 nanosheet/Ni foam heterostructure shows a low transmission resistance at the catalyst/electrolyte surface. Water-soluble pollutants, especially oil-production related pollutants, are nowadays a major form of public-health-threatening environmental hazard. In this work, we report a new design of Ni based photoelectrocatalyst for the degradation of polyacrylamide (PAM), this particularly malignant by product of oil recovery can be decomposed into harmless product using the proposed method. Specifically, a full spectrum Sn 3 O 4 nanosheet/Ni foam heterostructure photoelectrocatalyst has been developed. The Ni foam not only supports, as a substrate, the Sn 3 O 4 nan-catalyst, but can also interact with the catalyst extending the absorption spectrum into the NIR range. Our heterostructure has exhibited an excellent photoelectrocatalytic activity, resulted from an enhanced efficiency of light harvesting, as well as the more stabilized photogenerated charge pairs, and a higher rate of charge transfer at the interface of hetero-material. [ABSTRACT FROM AUTHOR]

Great attention has been drawn to flexible and portable electronic devices, so it is important to develop flexible energy-storage devices. In this study, the porous Ni-Co-N nanosheets on flexible graphene paper (GP) are prepared by surface nitridation of NiCo 2 O 4 nanosheets. Compared with NiCo 2 O 4 /GP, Ni 3 N/GP and CoN/GP, Ni-Co-N/GP shows superior performance in terms of specific capacitance of 960 F/g (48.1 mF/cm2) at 4 A/g, rate performance (86% capacitance retention) and cycle life (the capacitance retention reaches 95% over 5000 cycles). The paper-based all-solid-state asymmetric supercapacitors (SCs) are manufactured based on Ni-Co-N/GP and chemical oxidized GP (graphene oxide paper, GOP), which exhibits excellent bendability, flexibility, editability. The flexible energy device shows an outstanding specific energy of 4.78 mWh/cm3 and excellent cycle life (89% capacitance retention after 8000 cycles). Image 1 • The results demonstrate that the Ni-Co-N/GP shows superior performance than NiCo 2 O 4 /GP, Ni 3 N/GP and CoN/GP. • The Ni-Co-N/GP||GOP had high volumetric energy density of 4.78 mWh/cm3 and excellent cycle life. • The assembled energy device exhibits excellent bendability, flexibility, editability. [ABSTRACT FROM AUTHOR]

A strain of Nocardia isolated from crude oil-contaminated soils in the Qinghai-Tibetan Plateau degrades nearly all components of crude oil. This strain was identified as Nocardia soli Y48, and its growth conditions were determined. Complete genome sequencing showed that N. soli Y48 has a 7.3 Mb genome and many genes responsible for hydrocarbon degradation, biosurfactant synthesis, emulsification and other hydrocarbon degradation-related metabolisms. Analysis of the clusters of orthologous groups (COGs) and genomic islands (GIs) revealed that Y48 has undergone significant gene transfer events to adapt to changing environmental conditions (crude oil contamination). The structural features of the genome might provide a competitive edge for the survival of N. soli Y48 in oil-polluted environments and reflect the adaptation of coexisting bacteria to distinct nutritional niches. [ABSTRACT FROM AUTHOR]

The kk-center clustering is one of the well-studied clustering problems in computer science. We are given a set of data points P⊆RdP⊆Rd, where RdRd is dd dimensional Euclidean space. We need to select k≤|P|k≤|P| points as centers and partition the set PP into kk clusters with each point connecting to its nearest center. The goal is to minimize the maximum radius. We consider the so-called online kk-center clustering model where the data points in RdRd arrive over time. We present the bi-criteria (nk,(logU∗L∗)2)(nk,(log⁡U∗L∗)2)-competitive algorithm and (nk,logγlognγk)(nk,log⁡γlog⁡nγk)-competitive algorithm for semi-online and fully-online kk-center clustering respectively, where U∗U∗ is the maximum cluster radius of optimal solution, L∗L∗ is the minimum distance of two distinct points of PP, γγ is the ratio of the maximum distance of two distinct points and the minimum distance of two distinct points of PP and nn is the number of points that will arrive in total. [ABSTRACT FROM AUTHOR]

In this study, a series of innovative red-emitting Sm3+-doped K 5 La(MoO 4) 4 phosphors were synthesized using the solid-state reaction method. The X-ray powder diffraction patterns and Rietveld refinement confirmed the single-phase structure of the synthesized K 5 La(MoO 4) 4 :Sm3+ samples with trigonal system (space group R 3 ‾ m (#166)). The phosphors demonstrated a strong red emission at 644 nm, corresponding to the electric dipole transition 4G 5/2 → 6H 9/2 of Sm3+ ions. The optimal doping concentration for K 5 La (1- x) (MoO 4) 4 : x Sm3+ was found to be approximately 5 mol%. The temperature-dependent emission of phosphors was examined and found that the luminescence intensity remained at 86 % even at 480 K, showing the exceptional thermal stability of this material. K 5 La (1- x) (MoO 4) 4 : x Sm3+ phosphors displayed remarkable color stability with chromaticity coordinates falling within the red region in 1931 CIE diagram. K 5 La(MoO 4) 4 :5 mol%Sm3+ exhibited a high color purity of 99.9 % and internal quantum efficiency (IQE) was measured as 66.8 %. Light-emitting diodes (LEDs) were constructed using InGaN chips and the synthesized red phosphors. The chromaticity coordinates of the fabricated w-LED (white light-emitting diode) were (0.330, 0.351), closely resembling the typical white point of the National Television System Committee (NTSC) at (0.333, 0.333). The color rendering index (CRI, R a) and correlated color temperature (CCT) of w-LED were 87 and 5627 K. These findings strongly suggest the potential use of K 5 La(MoO 4) 4 :Sm3+ phosphors as red phosphors in LEDs. • K 5 La(MoO 4) 4 :Sm3+ phosphors are firstly synthesized via solid-state reaction. • The phosphor emits bright red light excited by 403 nm. • The phosphor exhibits good thermostability, high internal quantum efficiency and high color purity. • K 5 La(MoO 4) 4 :Sm3+ phosphors have potential to be used for w-LED with a high R a (87). [ABSTRACT FROM AUTHOR]

This document is an editorial preface for a special issue of the journal Mathematical Structures in Computer Science. The special issue focuses on the theory and applications of models of computation, specifically optimization theory and algorithms. The issue includes six papers that cover topics in both discrete and continuous optimization. The guest editors hope that the contributions in this special issue will stimulate and strengthen readers' interest in learning and researching optimization theory and algorithms. The papers in the special issue have undergone rigorous reviews by experts in the field. [Extracted from the article]

• City-wide park use was assessed before and after the COVID-19 shutdown. • Analysis included mobility data and fixed effects regression analysis. • Pandemic shutdown increased the likelihood of park visits from local block groups. • Time spent in parks and distance traveled to them decreased post pandemic. • Higher median household income was associated with stronger pandemic effects. Access to parks is important for a population's mental, physical, and social health. The importance of parks became even more apparent during the COVID-19 pandemic when publicly accessible outdoor spaces were needed to relax, exercise, and socialize. Using metropolitan Atlanta, Georgia as a case study, this study employs 207,785 rows of park visitation data to assess the spatial distribution of park users within 109 Atlanta parks for the year before and after the initial COVID-19 shutdown, focusing on the length of time spent in parks, distance of travel to get there, and quantity of visits. These facets are compared to the socio-demographic information of the park users to assess how different populations benefited from greenspace use. Furthermore, we compared site usage to park typologies to understand changes in park use. Results reveal that after the COVID-19 declaration, parks were more likely to be used among local block group populations, and the time spent in parks slightly decreased. Yet, the impact of COVID-19 on park use was less strong for lower income groups. Findings reveal the important role of parks during the pandemic and may guide future efforts to develop these public greenspace facilities. [ABSTRACT FROM AUTHOR]

Background: Exercise can promote sustainable protection against cold and warm liver ischemia–reperfusion injury (IRI) and tumor metastases. We have shown that this protection is by the induction of hepatic mitochondrial biogenesis pathway. In this study, we hypothesize that ZLN005, a PGC-1α activator, can be utilized as an alternative therapeutic strategy. Methods: Eight-week-old mice were pretreated with ZLN005 and subjected to liver warm IRI. To establish a liver metastatic model, MC38 cancer cells (1 × 106) were injected into the spleen, followed by splenectomy and liver IRI. Results: ZLN005-pretreated mice showed a significant decrease in IRI-induced tissue injury as measured by serum ALT/AST/LDH levels and tissue necrosis. ZLN005 pretreatment decreased ROS generation and cell apoptosis at the site of injury, with a significant decrease in serum pro-inflammatory cytokines, innate immune cells infiltration, and intrahepatic neutrophil extracellular trap (NET) formation. Moreover, mitochondrial mass was significantly upregulated in hepatocytes and maintained after IRI. This was confirmed in murine and human hepatocytes treated with ZLN005 in vitro under normoxic and hypoxic conditions. Additionally, ZLN005 preconditioning significantly attenuated tumor burden and increased the percentage of intratumoral cytotoxic T cells. Conclusions: Our study highlights the effective protection of ZLN005 pretreatment as a therapeutic alternative in terms of acute liver injury and tumor metastases. [ABSTRACT FROM AUTHOR]