Tuning social interactions' strength drives collective response to light intensity in schooling fish.

Schooling fish heavily rely on visual cues to interact with neighbors and avoid obstacles. The availability of sensory information is influenced by environmental conditions and changes in the physical environment that can alter the sensory environment of the fish, which in turn affects individual and group movements. In this study, we combine experiments and data-driven modeling to investigate the impact of varying levels of light intensity on social interactions and collective behavior in rummy-nose tetra fish. The trajectories of single fish and groups of fish swimming in a tank under different lighting conditions were analyzed to quantify their movements and spatial distribution. Interaction functions between two individuals and the fish interaction with the tank wall were reconstructed and modeled for each light condition. Our results demonstrate that light intensity strongly modulates social interactions between fish and their reactions to obstacles, which then impact collective motion patterns that emerge at the group level.

Ruthenium Complexes with NNN-Pincer Ligands for N-Methylation of Amines Using Methanol.

A series of ruthenium complexes (Ru1-Ru4) bearing new NNN-pincer ligands were synthesized in 58-78% yields. All of the complexes are air and moisture stable and were characterized by IR, NMR, and high-resolution mass spectra (HRMS). In addition, the structures of Ru1-Ru3 were confirmed by X-ray crystallographic analysis. These Ru(II) complexes exhibited high catalytic efficiency and broad functional group tolerance in the N-methylation reaction of amines using CH3OH as both the C1 source and solvent. Experimental results indicated that the electronic effect of the substituents on the ligands considerably affects the catalytic reactivity of the complexes in which Ru3 bearing an electron-donating OMe group showed the highest activity. Deuterium labeling and control experiments suggested that the dehydrogenation of methanol to generate ruthenium hydride species was the rate-determining step in the reaction. Furthermore, this protocol also provided a ready approach to versatile trideuterated N-methylamines under mild conditions using CD3OD as a deuterated methylating agent.

Bridging Component Strategy in Phosphomolybdate-Based Sensors for Electrochemical Determination of Trace Cr(VI).

Rapid and sensitive electrochemical determination of trace carcinogenic Cr(VI) pollutants remains an urgent and important task, which requires the development of active sensing materials. Herein, four cases of reduced phosphomolybdates with formulas of the (H2bib)3[Zn(H2PO4)]2{Mn[P4Mo6O31H7]2}·6H2O (1), (H2bib)2[Na(H2O)]2[Mn(H2O)]2{Mn[P4Mo6O31H6]2}·5H2O (2), (H2bib)3[Mo2(µ2-O)2(H2O)4]2{Ni[P4Mo6O31H2]2}·4H2O (3), and (H2bib)2{Ni[P4Mo6O31H9]2}·9H2O (4) (bib = 4,4'-bis(1-imidazolyl)-biphenyl) were hydrothermally synthesized under the guidance of a bridging component strategy, which function as effective electrochemical sensors to detect trace Cr(VI). The difference of hybrids 1-4 is in the inorganic moiety, in which the reduced phosphomolybdates {M[P4MoV6O31]2} (M{P4Mo6}2) exhibited different arrangements bridged by different cationic components ({Zn(H2PO4)} subunit for 1, [Mn2(H2O)2]4+ dimer for 2, and [MoV2(µ2-O)2(H2O)4]6+ for 3). As a result, hybrids 1 and 3 display noticeable Cr(VI) detection activity with low detection limits of 14.3 nM (1.48 ppb) for 1 and 6.61 nM (0.69 ppb) for 3 and high sensitivities of 97.3 and 95.3 µA·mM-1, respectively, which are much beyond the World Health Organization's detection threshold (0.05 ppm) and superior to those of the contrast samples (inorganic Mn{P4Mo6}2 salt and hybrid 4), even the most reported noble-metal catalysts. This work supplies a prospective pathway to build effective electrochemical sensors based on phosphomolybdates for environmental pollutant treatment.

Noise-Induced Quenched Disorder in Dense Active Systems.

We report and characterize the emergence of a noise-induced state of quenched disorder in a generic model describing a dense sheet of active polar disks. In this state, self-propelled disks become jammed with random orientations, only displaying small fluctuations about their mean positions and headings. The quenched disorder phase appears at intermediate noise levels, between moving polar order and standard dynamic disorder. We show that it results from retrograde forces produced by angular fluctuations with Ornstein-Uhlenbeck dynamics, compute its critical noise, and argue that it could emerge in a variety of systems.

The impact of individual perceptual and cognitive factors on collective states in a data-driven fish school model.

In moving animal groups, social interactions play a key role in the ability of individuals to achieve coordinated motion. However, a large number of environmental and cognitive factors are able to modulate the expression of these interactions and the characteristics of the collective movements that result from these interactions. Here, we use a data-driven fish school model to quantitatively investigate the impact of perceptual and cognitive factors on coordination and collective swimming patterns. The model describes the interactions involved in the coordination of burst-and-coast swimming in groups of Hemigrammus rhodostomus. We perform a comprehensive investigation of the respective impacts of two interactions strategies between fish based on the selection of the most or the two most influential neighbors, of the range and intensity of social interactions, of the intensity of individual random behavioral fluctuations, and of the group size, on the ability of groups of fish to coordinate their movements. We find that fish are able to coordinate their movements when they interact with their most or two most influential neighbors, provided that a minimal level of attraction between fish exist to maintain group cohesion. A minimal level of alignment is also required to allow the formation of schooling and milling. However, increasing the strength of social interactions does not necessarily enhance group cohesion and coordination. When attraction and alignment strengths are too high, or when the heading random fluctuations are too large, schooling and milling can no longer be maintained and the school switches to a swarming phase. Increasing the interaction range between fish has a similar impact on collective dynamics as increasing the strengths of attraction and alignment. Finally, we find that coordination and schooling occurs for a wider range of attraction and alignment strength in small group sizes.

Copper Complexes with N,N,N-Tridentate Quinolinyl Anilido-Imine Ligands: Synthesis and Their Catalytic Application in Chan-Lam Reactions.

The treatment of 2-(ArNC(H))C6H4-HNC9H6N with n-BuLi and the subsequent addition of CuCl2 afforded the anilido-aldimine Cu(II) complexes 1-5 Cu[{2-[ArN=C(H)]C6H4}N(8-C9H6N)]Cl (Ar = 2,6-iPr2C6H3 (1), 2,4,6-(CH3)3C6H2 (2), 4-OCH3C6H4 (3), 4-BrC6H4 (4), 4-ClC6H4 (5)), respectively. All the copper complexes were fully characterized by IR, EPR and HR-MS spectra. The X-ray diffraction analysis reveals that 2 and 4 are mononuclear complexes, and the Cu atom is sitting in a slightly square-planar geometry. These Cu(II) complexes have exhibited excellent catalytic activity in the Chan-Lam coupling reactions of benzimidazole derivatives with arylboronic acids, achieving the highest yields of up to 96%.

Dehydrogenative Synthesis of Quinolines and Quinazolines via Ligand-Free Cobalt-Catalyzed Cyclization of 2-Aminoaryl Alcohols with Ketones or Nitriles.

We present a convenient and efficient protocol to synthesize quinolines and quinazolines in one pot under mild conditions. A variety of substituted quinolines were synthesized in good to excellent yields (up to 97% yield) from the dehydrogenative cyclizations of 2-aminoaryl alcohols and ketones catalyzed by readily available Co(OAc)2·4H2O. This cobalt catalytic system also showed high activity in the reactions of 2-aminobenzyl alcohols with nitriles, affording various quinazoline derivatives (up to 95% yield). The present protocol offers an environmentally benign approach for the synthesis of N-heterocycles by employing an earth-abundant cobalt salt under ligand-free conditions.

Polyoxometalate-Incorporated Metal-Organic Network as a Heterogeneous Catalyst for Selective Oxidation of Aryl Alkenes.

Selective oxidation of aryl alkenes is important for chemical synthesis reactions, in which the key lies in the rational design of efficient catalysts. Herein, four polyoxometalate (POM)-incorporated metal-organic networks, with the formulas of [Co(ttb)(H2O)3]2[SiMo12O40]·2H2O (1), [Co(ttb)(H2O)2]2[SiW12O40]·8H2O (2), [Zn(Httb)(H2ttb)][BW12O40]·9H2O (3) and {[Zn(H2O)3(ttb)]4[Zn3(H2O)6]}[H3SiW10.5Zn1.5O40]2·24H2O (4) (ttb = 1,3,5-tri(1,2,4-triazol-1-ylmethyl)-2,4,6-trimethylbenzene), were hydrothermally synthesized and structurally characterized. Structural analysis showed that compound 1 consists of a POM-encapsulated three-dimensional (3-D) supramolecular framework; compound 2 is composed of a POM-supported 3-D coordination network; and compounds 3-4 show POM-incorporated 3-D supramolecular networks. Using selective catalytic oxidation of styrene as the model reaction, compounds 1-4 as heterogeneous catalysts display excellent performance with the double advantages of high styrene conversion and benzaldehyde selectivity owing to the synergistic effect among POM anions and transition metal (TM) centers. Among them, compound 1 exhibits the highest performance with ca. 96% styrene conversion and ca. 99% benzaldehyde selectivity in 3 h. In addition, compound 1 also displays excellent substrate compatibility, good reusability, and structural stability. Thus, a plausible reaction pathway for the selective oxidation of styrene is proposed. This study on the structure-function relationship paves a way for the rational design of POM-based heterogeneous catalysts for important catalysis applications.

Three-Dimensional Silver-Containing Polyoxotungstate Frameworks for Photocatalytic Aerobic Oxidation of Benzyl Alcohol.

Photocatalytic organic transformation derived by functionalized polyoxometalate (POM)-based metal-organic frameworks provides a feasible route for fine chemical synthesis. Herein, three kinds of photoactive three-dimensional silver-containing polyoxotungstate frameworks are synthesized with the formulas [Ag3L2(OH)][Na(H2O)0.5][PW12O40]·H2O (1), [Ag4L3][SiW12O40] (2), and [Ag(H2O)][Ag4L3][BW12O40]·9H2O (3) (L = 1,4-di(4H-1,2,4-triazol-4-yl)benzene). In compounds 1-3, the cationic Ag-triazole clusters with diverse nuclei serve as nodes to assemble with rigid bridging ligands (L) and polyoxoanions to extend into stable three-dimensional frameworks, in which Keggin-type anions act as guests or pendants. When using them as heterogeneous photocatalysts, compounds 1-3 show high catalytic activity and selectivity for the photocatalytic aerobic oxidation of benzyl alcohol to benzoic acid under 10 W 365 nm light irradiation. Among them, compound 1 exhibits the highest performance with ca. 99% benzyl alcohol conversion and 99% selectivity of benzoic acid in 9 h. Compounds 2 and 3 show ca. 79 and 88% conversions of benzyl alcohol, respectively, which are higher than those of the individual Keggin-type precursors. Moreover, mechanism investigation suggests that the synergistic cooperation occurring between cationic Ag-triazole clusters and Keggin-type polyoxoanions modulates the energy band structures of compounds 1-3, resulting in the efficient separation of photogenerated carriers and accelerating the aerobic oxidation of benzyl alcohol. This work provides some important guidance for the design and development of efficient POM-based photocatalysts for practical organic transformation.

Bifunctional Sensors Based on Phosphomolybdates for Detection of Inorganic Hexavalent Chromium and Organic Tetracycline.

Exploring effective sensors for detecting possible hazards in a water system are greatly significant. This work proposed a strategy for stable and effective bifunctional sensors via incorporating hourglass-type phosphomolybdates into metal-organic fragments to construct a high-dimensional framework. Two hourglass-type phosphomolybdate-based electrochemical sensors toward heavy metal ion Cr(VI) and tetracycline (TC) detection were designed with the formula [CoII2(H2O)4NaI2][CoII(Hbpe)][NaI(bpe)1.5]{CoII[PV4MoV6O31H6]2}·9H2O (1) and [CoII(H2O)4NaI3][CoII(Hbpe)][CoII(bpe)]{CoII[PV4MoV6O31H6]2}·9H2O (2) [bpe = 1,2-di(4-pyridyl)ethylene]. Structural analysis showed that hybrids 1 and 2 possess three-dimensional POM-supported network features with favorable stability and exhibit reversible redox properties. Experiments found that this kind of hybrids as efficient sensors have excellent electrochemical performance toward Cr(VI) detection with high sensitivities of 0.111 µA·µM-1 for 1 and 0.141 µA·µM-1 for 2, fast response time of 1 s, and low detection limits of 30 nM for 1 and 27 nM for 2, which far meet the standard of WHO for drinking water. Moreover, hybrids 1-2 also exhibit fast responses to TC detection with sensitivities of 0.0073 and 0.022 µA·mM-1 and detection limits of 0.426 and 0.084 mM. This work offers a novel strategy for the purposeful design of efficient POM-based electrochemical sensors for accurate determination of contaminants in a practical water system.

Climate network approach reveals the modes of CO2 concentration to surface air temperature.

Increasing atmospheric carbon dioxide (CO2) is expected to be the main factor of global warming. The relation between CO2 concentrations and surface air temperature (SAT) has been found related to Rossby waves based on a multi-layer complex network approach. However, the significant relations between CO2 and SAT occur in the South Hemisphere that is not that much influenced by human activities may offer not enough information to formulate targeted carbon reduction policies. Here, we address it by removing the effects of the Rossby waves to reconstruct CO2 concentrations and SAT multi-layer complex network. We uncover that the CO2 concentrations are strongly associated with the surrounding SAT regions. The influential regions of CO2 on SAT occur over eastern Asia, West Asia, North Africa, the coast of North American, and Western Europe. It is shown that CO2 over Siberia in phase with the SAT variability in eastern East Asia. Indeed, CO2 concentration variability is causing effects on the recent warming of SAT in some middle latitude regions. Furthermore, sensitive parameters that CO2 impacts SAT of top 15 carbon emissions countries have been identified. These countries are significantly responsible for global warming, giving implications for carbon emissions reductions. The methodology and results presented here not only facilitate further research in regions of increased sensitivity to the warming resulting from CO2 concentrations but also can formulate strategies and countermeasures for carbon emission and carbon reduction.

Collective Motion and Self-Organization of a Swarm of UAVs: A Cluster-Based Architecture.

This study proposes a collective motion and self-organization control of a swarm of 10 UAVs, which are divided into two clusters of five agents each. A cluster is a group of UAVs in a dedicated area and multiple clusters make a swarm. This paper designs the 3D model of the whole environment by applying graph theory. To address the aforesaid issues, this paper designs a hybrid meta-heuristic algorithm by merging the particle swarm optimization (PSO) with the multi-agent system (MAS). First, PSO only provides the best agents of a cluster. Afterward, MAS helps to assign the best agent as the leader of the nth cluster. Moreover, the leader can find the optimal path for each cluster. Initially, each cluster contains agents at random positions. Later, the clusters form a formation by implementing PSO with the MAS model. This helps in coordinating the agents inside the nth cluster. However, when two clusters combine and make a swarm in a dynamic environment, MAS alone is not able to fill the communication gap of n clusters. This study does it by applying the Vicsek-based MAS connectivity and synchronization model along with dynamic leader selection ability. Moreover, this research uses a B-spline curve based on simple waypoint defined graph theory to create the flying formations of each cluster and the swarm. Lastly, this article compares the designed algorithm with the NSGA-II model to show that the proposed model has better convergence and durability, both in the individual clusters and inside the greater swarm.

A Bicadmium-Substituted Polyoxometalate Network Based on a Vanadosilicate Cluster for the Selective Oxidation of Styrene to Benzaldehyde.

A new bicadmium-substituted vanadosilicate, [Cd(en)2]2[(en)2Cd2Si8V12O40(OH)8(H2O)0.5]·5H2O (1; en = ethylenediamine), had been hydrothermally synthesized and characterized. Structural analysis revealed that the kind of new [(en)2Cd2Si8V12O40(OH)8(H2O)0.5]4- polyoxoanionic cluster was derived from the classical {V18O42} cluster by replacing six {VO5} square pyramids with four {Si2O7} and two [Cd(en)]2+ groups. Notably, such mixed substitution of both main-group and transition metals in polyoxovanadates is much less developed. Furthermore, compound 1 displays efficient catalytic activity toward the selective oxidation of styrene to benzaldehyde with a conversion of 97% and a selectivity of 87% in 8 h.

Investigating time, strength, and duration of measures in controlling the spread of COVID-19 using a networked meta-population model.

Policy makers around the world are facing unprecedented challenges in making decisions on when and what degrees of measures should be implemented to tackle the COVID-19 pandemic. Here, using a nationwide mobile phone dataset, we developed a networked meta-population model to simulate the impact of intervention in controlling the spread of the virus in China by varying the effectiveness of transmission reduction and the timing of intervention start and relaxation. We estimated basic reproduction number and transition probabilities between health states based on reported cases. Our model demonstrates that both the time of initiating an intervention and its effectiveness had a very large impact on controlling the epidemic, and the current Chinese intense social distancing intervention has reduced the impact substantially but would have been even more effective had it started earlier. The optimal duration of the control measures to avoid resurgence was estimated to be 2 months, although would need to be longer under less effective controls.

Reduced Phosphomolybdate Hybrids as Efficient Visible-Light Photocatalysts for Cr(VI) Reduction.

Photocatalytic reduction of hexavalent chromium [Cr(VI)] is a promising technology approach to highly efficiently and environmentally tackle the problem of Cr(VI) pollution, in which the key challenge is in the development of effective photocatalysts. In this work, highly reduced hourglass-type molybdophosphate hybrids with the formulas [Zn(mbpy)(H2O)2]2[Zn(mbpy)(H2O)]2{Zn[P4Mo6O31H7]2}·9H2O (1), [Na(H2O)2]2[Zn(mbpy)(H2O)]2[Zn(mbpy)(H2O)2]2{Zn[P4Mo6O31H6]2}·15H2O (2), and (H2mbpy){[Zn(mbpy)(H2O)]2[Zn(H2O)]2}{Zn[P4Mo6O31H6]2}·10H2O (3) (mbpy = 4,4'-dimethyl-2,2'-bipyridine) have been hydrothermally synthesized and used as photocatalysts for the reduction of Cr(VI) under mild conditions. Structural analysis showed that the inorganic moieties in crystals 1-3 are composed of a unique 0D single cluster form, a 1D chainlike structure, and a 2D-layered structure, respectively, in which polyanions were constructed by hourglass-type molybdophosphates with one Zn(II) ion as the central metal. These hybrids displayed good performance for the photocatalytic reduction of Cr(VI) by virtue of their wide visible-light adsorption, suitable energy band structures, and specific spatial arrangements of polyanionic species. Among them, hybrid 2 exhibits the best photocatalytic performance with a Cr(VI) reduction conversion rate of almost 94.7% within 180 min of reaction time. The photocatalysis mechanism investigation revealed that highly reduced hourglass-type molybdophosphate clusters can be illuminated by visible light. The photoinduced electrons induced by hourglass-type polyanions can directly reduce Cr(VI) to Cr(III), while the photogenerated holes are used to oxidize the sacrificial agent isopropyl alcohol to acetone. This work provides new guidance for the design and preparation of highly efficient photocatalysts for the reduction of Cr(VI).

Krebs-Type {M2(WO2)2[B-ß-SbW9O33]2}n- (M = SbIII, (WO3)) Tungstoantimonate Possessing Unique Pseudo-Seesaw Sb-O Structure.

Two new Krebs-type tungstoantimonates (H2en)8H6{[Sb2(WO2)2(B-ß-SbW9O33)2][(WO2)2(WO3)2(B-ß-SbW9O33)2]}·22H2O (1) and (H2en)7[(WO2)2(WO3)2(B-ß-SbW9O33)2]·12H2O (2) were synthesized and characterized. Notably, crystal 1 possesses a specific pseudo-seesaw SbO4 subunit in the central metal belt of [Sb2(WO2)2(B-ß-SbW9O33)2]12- species, which is rare in reported Krebs-type polyoxometalates. One of the structural features is that there are two kinds of Krebs-type polyanionic clusters in crystal 1 labeled as {(WO2)2(WO3)2(B-ß-SbW9O33)2} (part A) and {Sb2(WO2)2(B-ß-SbW9O33)2} (part B), respectively. The subunits A and B are alternately connected through Sb-O-W bonds into a chain-like structure of inorganic clusters. Moreover, the catalytic property of crystals 1 and 2 for electron-transfer reaction were investigated by transferring K3[Fe(CN)6] into K4[Fe(CN)6].

Identifying influential neighbors in animal flocking.

Schools of fish and flocks of birds can move together in synchrony and decide on new directions of movement in a seamless way. This is possible because group members constantly share directional information with their neighbors. Although detecting the directionality of other group members is known to be important to maintain cohesion, it is not clear how many neighbors each individual can simultaneously track and pay attention to, and what the spatial distribution of these influential neighbors is. Here, we address these questions on shoals of Hemigrammus rhodostomus, a species of fish exhibiting strong schooling behavior. We adopt a data-driven analysis technique based on the study of short-term directional correlations to identify which neighbors have the strongest influence over the participation of an individual in a collective U-turn event. We find that fish mainly react to one or two neighbors at a time. Moreover, we find no correlation between the distance rank of a neighbor and its likelihood to be influential. We interpret our results in terms of fish allocating sequential and selective attention to their neighbors.

Synthesis of Hybrid Phosphomolybdates and Application as Highly Stable and Effective Catalyst for the Reduction of Cr(VI).

Three hybrid phosphomolybdates were successfully synthesized by hydrothermal method and characterized by a series of physicochemical analysis techniques. X-ray single-crystal structural analysis revealed that three compounds with the reductive polyanionic clusters (MoV) were wrapped by protonated organic component bpp cations (bpp = 1,3-bi(4-pyridyl)propane) through the complex supramolecular hydrogen bonding network. They also have similar molecular formulas: (H2bpp)3[PbM(H2O)2]2H6{M[Mo6O12(OH)3(HPO4)3(PO4)]2}2· nH2O (M = Fe in 1, Zn in 2, n = 4; or M = Mn in 3, n = 6). The oxidation states of all Mo centers in these polyanions are in the form of +5, presenting clusters with the higher negative charge. The feature showed that they were easy to be modified by transition metal and organic moieties, so as to form a high-dimensional structure and produce functional materials with specific properties. Comparison of catalytic ability of three crystals to reduce CrVI using formic acid as reductant, found that crystal 1 was effectively active to this redox reaction. The conversion of CrVI can reach 99% after 120 min of heating in 55 °C water bath, and the conversion of above 95% can still be achieved after 5 recycles of applications.

Polyanionic Clusters [M(P4Mo6)2] (M = Ni, Cd) as Effective Molecular Catalysts for the Electron-Transfer Reaction of Ferricyanide to Ferrocyanide.

Three polyanion-containing supramolecular hybrids, (H2bpp)6{Ni[Mo(V)6O13(OH)2(HPO4)3(H2PO4)]2}2·13H2O [1; bpp = 1,3-bis(4-pyridyl)propane], (H2bpp)5{Cd[Mo(V)6O15(HPO4)3(H2PO4)]2}{Cd[Mo(V)6O15(HPO4)4]2}·10H2O (2), (H2bpp)2[Cd(H2O)Cd(H2O)2]2{Cd[Mo(V)6O12(OH)3(HPO4)2(PO4)2]2}·8H2O (3), have been synthesized and characterized. The inorganic moieties in 1-3 belong to the reduced {M[P4Mo(V)6X31]2}(n-) (M = Ni, Cd) clusters. Three supramolecular hybrids exhibit reversible multiple electron-transfer behaviors and have been used as heterogeneous molecular catalysts for the reduction of ferricyanide (Fe(III)) to ferrocyanide (Fe(II)) with Na2S2O3 as a reductant. The experimental results indicate that hybrid materials 1-3 have higher catalytic activity toward the reaction. These low-cost catalysts can effectively decrease the activation energy of this reaction. These values are calculated to be 25.35 kJ·mol(-1) for hybrid 2, 84.11 kJ·mol(-1) for hybrid 1, and 83.14 kJ·mol(-1) for hybrid 3. The reaction mechanism is subjected to a surface-catalytic process.

Sandwich-Type Polyoxotungstate Consisting of Two Different Trilacunary Keggin-Type Units.

A unique mixed W/Sb/Mn/Ag sandwich-type metal-O cluster was isolated, in which the six-membered {Ag4O3[Mn(OH2)]2}2+ cationic belt is sandwiched between two different anionic slices: the trilacunary B-ß-[SbW9O33]9- and the central-atom-lost A-α-{[Mn(OH2)]2W7O32}18-.