Optimal control of effort of a stage structured prey–predator fishery model with harvesting

This paper describes a prey–predator fishery model with stage structure for prey. The adult prey and predator populations are harvested in the proposed system. The dynamic behavior of the model system is discussed. It is observed that singularity induced bifurcation phenomenon is appeared when variation of the economic interest of harvesting is taken into account. We have incorporated state feedback controller to stabilize the model system in the case of positive economic interest. Fishing effort used to harvest the adult prey and predator populations is used as a control to develop a dynamic framework to investigate the optimal utilization of the resource, sustainability properties of the stock and the resource rent earned from the resource. Pontryagin’s maximum principle is used to characterize the optimal control. The optimal system is derived and then solved numerically using an iterative method with Runge–Kutta fourth-order scheme. Simulation results show that the optimal control scheme can achieve sustainable ecosystem.     

Silica chloride (SiO2-Cl) catalyzed one pot synthesis of 2,3-disubstituted-thiazolidin-4-one

Abstract

In this paper, we report one-pot, three-component cyclo condensation of an aldehyde, an amine and thioglycolic acid to form 2,3-disubstituted-thiazolidin-4-one by using supported protic acid (Silica Chloride: SiO₂-Cl) catalyst. The catalyst SiO₂-Cl is compatible with a variety of aldehydes (aryl/heteroaryl) and the aromatic amines affording 2,3-disubstituted-thiazolidin-4-one analogs in 72–89% yields. Moreover, the supported catalyst was recycled several times without significant loss of catalytical activity     

Some case studies on application of “rm2” metrics for judging quality of quantitative structure–activity relationship predictions: Emphasis on scaling of response data

Quantitative structure–activity relationship (QSAR) techniques have found wide application in the fields of drug design, property modeling, and toxicity prediction of untested chemicals. A rigorous validation of the developed models plays the key role for their successful application in prediction for new compounds. The r_m² metrics introduced by Roy et al. have been extensively used by different research groups for validation of regression‐based QSAR models. This concept has been further advanced here with introduction of scaling of response data prior to computation of r_m². Further, a web application (accessible from http://aptsoftware.co.in/rmsquare/ and http://203.200.173.43:8080/rmsquare/ ) for calculation of the r_m² metrics has been introduced here. The present study reports that the web application can be easily used for computation of r_m² metrics provided observed and QSAR‐predicted data for a set of compounds are available. Further, scaling of response data is recommended prior to r_m² calculation. © 2013 Wiley Periodicals, Inc.     

Halogen Bonding in Two-Dimensional Crystal Engineering

Halogen bonds, which provide an intermolecular interaction with moderate strength and high directionality, have emerged as a promising tool in the repertoire of non-covalent interactions. In this review, we provide a survey of the literature where halogen bonding was used for the fabrication of supramolecular networks on solid surfaces. The definitions of, and the distinction between halogen bonding and halogen-halogen interactions are provided. Self-assembled networks formed at the solution/solid interface and at the vacuum-solid interface, stabilized in part by halogen bonding, are discussed. Besides the broad classification based on the interface at which the systems are studied, the systems are categorized further as those sustained by halogen-halogen and halogen-heteroatom contacts.     

Front Cover: Water-Solvation-Dependent Spin Transitions in Cobalt(II)-Octacyanidometallate Complexes (Eur. J. Inorg. Chem. 30/2023)

The spin-crossover (SCO) and charge-transfer (CT) phenomena, the switching processes between two distinguishable magnetic states, are promising for developing materials capable of sophisticated memory and sensing functionalities. The majority of SCO systems are based on iron(II) complexes. However, cobalt(II)-2,2′:6′,2′′-terpyridine (terpy) systems emerge as a promising alternative. In this work, new complex salts [Co^II(terpy)₂]₂[Mo^IV(CN)₈] ⋅ 15H₂O, Co₂Mo (H₂O), and [Co^II(terpy)₂]₃[W^V(CN)₈]₂ ⋅ 12H₂O, Co₃W₂ (H₂O) were synthesized and physiochemically characterized. Structural studies for both compounds revealed [Co(terpy)₂]²⁺ layers pillared by octacyanidometallate anions and completed with water molecules between them. Magnetic studies confirmed that the (de)solvated phases of both complexes exhibit partial SCO on the cobalt(II) centers: Co^II−LS (S_Co(II)-LS=¹/₂)↔Co^II−HS (S_Co(II)-HS=³/₂). Moreover, handling dehydrated samples in a high-humidity environment leads to partial recovery of previous magnetic properties via humidity-induced SCO for Co₂Mo : Co^II−HS→Co^II−LS, and the new phenomenon of isothermal humidity-activated charge-transfer-induced spin transition, which we define here as HACTIST, for Co₃W₂ : Co^II−HS⋅⋅⋅W^V (S_Co(II)-HS=³/₂ and S_W(V)=¹/₂)→Co^III−LS⋅⋅⋅W^IV (S_W(IV)=0 and S_Co(III)-LS=0). These comprehensive studies shed light on the water-solvation-dependent spin transitions in Co(II)-octacyanidometallate(IV/V) complexes.     

Modelling and analysis of a multiple delayed exploited ecosystem towards coexistence perspective

This paper describes a multiple delayed modified Leslie–Gower type predator–prey system with a strong Allee effect in prey population growth. Non-selective effort is used to harvest the population. The dynamical characteristics of the delay induced system are rigorously studied using mathematical tools. The existence of coexistence equilibria is ensured, and the dynamic behavior of the system is investigated around coexistence equilibria. Uniform strong persistence and permanence of the system are discussed in order to ensure long-term survival of the species. The stability of the delay preserved system is investigated. Sufficient conditions are derived for local and global stability of the system. The existence of Hopf bifurcation phenomenon is examined around interior equilibria of the system. Subsequently, we use normal form method and center manifold theorem to examine the nature of the Hopf bifurcation. Finally, numerical simulations are carried out to validate the analytical findings.     

Effort dynamics of a delay-induced prey–predator system with reserve

This paper describes a prey?Cpredator fishery system with prey dispersal in a two-patch environment, one of which is a free fishing zone and the other a protected zone. The proposed system reflects the dynamic interaction between the net economic revenue and the fishing effort used to harvest the population in presence of a suitable tax. Local as well as global stability of the system is analyzed. The optimal taxation policy is formulated and solved with the help of Pontryagin??s maximal principle. The objective of the paper is to achieve the sustainability of the fishery, keeping the ecological balance, and maximize the monetary social benefit. The dynamical behavior of the delay system is further analyzed through incorporating discrete type gestational delay of predators, and the existence of Hopf bifurcation phenomenon is checked at the interior equilibrium point. Moreover, we use normal form method and center manifold theorem to examine the nature of the Hopf bifurcation. Theoretical results are verified with the help of numerical examples and graphical illustrations.     

Molecular structural analysis of noncarious cervical sclerotic dentin using Raman spectroscopy

Molecular structure of the sclerotic dentin in noncarious cervical lesions (NCCLs) including both the inorganic phase and organic phase was investigated using Raman spectroscopy. It was found that NCCL sclerotic dentin was hypermineralized with the mineral/matrix ratios 2–3 times higher than those of normal dentin, which was caused by both the increase of mineral content and decrease of organic matrix (collagen) content in the sclerotic dentin. For the inorganic phase, the phosphate band (PO₄³⁻, ν₁, symmetric stretching vibrational mode) in NCCL sclerotic dentin was shifted from 960 to 963 cm⁻¹, and the width of this band was decreased from 16.4 to 10.4 cm⁻¹, indicating that the degree of mineral crystallinity in NCCL sclerotic dentin was higher than that of normal dentin. In addition, the carbonate content in the mineral of NCCL sclerotic dentin was less than that of normal dentin. As compared to the inorganic phase, the changes within the organic phase were not dramatic. However, the changes in collagen cross‐link density along with other spectral changes were still detectable. There was a noteworthy reduction in the ratio of nonreducible to reducible cross‐links in the NCCL sclerotic dentin, indicating that cross‐link breaks occurred in the collagen matrix of the lesions. Copyright © 2009 John Wiley & Sons, Ltd.