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The linear features and phenomena concerning head-on collision between the two ion acoustic solitary waves are investigated considering the multi-component plasma system comprising singly charged c...

The characteristic behaviour of breathers as well as N-order Rogue wave (RW) solution in homogeneous unmagnetized electron-positron-ion plasmas (consisting of cold ions, and isothermal Maxwellian electrons and positrons) has been studied theoretically. Nonlinear Schrödinger (NLS) equation is derived employing Krylov-Bogoliubov-Mitropolosky (KBM) perturbation technique in solving the concerned problems. The analytical solution of the NLS equation in the forms of breathers such as Akhmediev breather (AB), Kuznetsov-Ma breather (KM) solitons, as well as first-, second-, third-, and fourth-order RWs solution are obtained. The characteristic behaviour of breathers’ and their dependency on the relevant physical parameters are examined. The different orders of RWs are analyzed to obtain the region of existence of ion acoustic (IA) rogue waves (IARWs) with respect to unstable region. The potential profiles concerning different orders of RWs depend on the ratio of positron to electron concentrations ( ρ ) and wave number ( k ). Analysis reveals that the spatial difference between the two adjacent peaks of AB profiles are increasing with the enhancement of transformer physical parameter ( Λ ), while the temporal evolution between the two neighboring peaks of KM profiles decreases with increasing Λ and the amplitudes become large as well. The amplitudes of first-, second-, and third-order RWs profiles are decreasing with increasing ρ while the amplitude of fourth-order RWs profile is increasing. The results obtained in this study may be useful in understanding the propagation of nonlinear waves in optical fibers, Bose-Einstein condensates, plasma physics and atmospheric physics.

We discuss congruences of p-algebras. We characterize kernel ideals of a p-algebra. Indeed, we show that an ideal of a p-algebra is a p-ideal if and only if it is a kernel ideal. We study cokernel filters of a p-algebra. We construct a class of p-algebras in which every cokernel filter is a p-filter. We also give some characterizations of Boolean congruences of a p-algebra.

A meet semilattice with a partial join operation satisfying some axioms is a JP-semilattice. A PJP-semilattice is a pseudocomplemented JP-semilattice. We characterize Stone JP-semilattices, give some characterizations of kernel ideals of a Stone JP-semilattice, and describe the join of two kernel ideals of a Stone JP-semilattice.

While every finite lattice-based algebra is dualisable, the same is not true of semilattice-based algebras. We show that a finite semilattice-based algebra is dualisable if all its operations are compatible with the semilattice operation. We also give examples of infinite semilattice-based algebras that are dualisable. In contrast, we present a general condition that guarantees the inherent non-dualisability of a finite semilattice-based algebra. We combine our results to characterise dualisability amongst the finite algebras in the classes of flat extensions of partial algebras and closure semilattices. Throughout, we emphasise the connection between the dualisability of an algebra and the residual character of the variety it generates.

This paper is both a contribution to natural duality theory as it applies to varieties of Heyting algebras and to the theory of standard topological quasi-varieties (see [3]) in general. We prove that the n-element Heyting chain C n has an alter ego, consisting of n−2 endomorphisms, that yields an optimal duality on the variety generated by C n . In the case n = 4, we give a set of quasi-equations that describe the dual category. We also give a set of quasi-equations that describe the strong dual category that is obtained by adding a partial endomorphism of C 4 to the type of the alter ego. A quasi-equational description of the optimal dual category for the variety of Heyting algebras generated by $${\bf 2}^{2} \oplus {\bf 1}$$ is also given. En route, we prove that if a finite topological unary algebra is injective amongst the finite algebras in the variety it generates, then it is standard. The results of [3] then allow us to give non-topological proofs of our topological descriptions of the dual categories.

The activation and stabilization of Chromobacterium viscosum lipase (glycerol-ester hydrolase, EC 3.1.1.3) by a simple pretreatment with acetone was studied in AOT/water/isooctane reverse micellar systems, using the hydrolysis of olive oil as a model reaction. The maximum activity of acetone treated lipase was found to be 160% higher than that of native lipase. These observations were rationalized by the assumption based on the lipase conformational changes accompanied by the enhancement of lipase surface with hydrophobic amino acids. The dependence of catalytic activity on the various parameters relevant to the pretreatment procedure such as acetone content, the pH of water–acetone solution, agitation time of the lipase in water–acetone solution and freeze-drying time were investigated. The change in lipase conformation due to the treatment with acetone was confirmed by typtophyl fluorescence spectroscopy as well as lipase microencapsulation methods in reverse micelles. The acetone treated lipase entrapped in AOT reverse micelles was very stable, retaining over 83% of its initial activity after 40 days, whereas the half-life of native lipase was 38 days.

The activity of Chromobacterium viscosum lipase for hydrolysis of olive oil in sodium bis-(2-ethylhexyl) sulfosuccinate (AOT) reverse micelles was increased by pretreatment with acetone. In contrast to the untreated lipase, no sharp fall in the activity of the treated lipase at higher W0 (water to AOT molar ratio) values was observed. The fluorescence emission intensity of the treated lipase in reverse micelles was higher than that of the untreated lipase but the maximal emission wavelength (λmax) was the same for both lipases. A kinetic model that considers the free substrate in equilibrium with the substrate adsorbed on the micellar surface was successfully used to better understand the activity enhancement. The Michaelis constant (Km) and substrate adsorption equilibrium constant (Kad) were reduced by lipase pretreatment with acetone whereas the maximum reaction rate (vmax) remained unaltered. Copyright © 2005 Society of Chemical Industry

The addition of short chain polyethylene glycols (PEGs) activated Chromobacterium viscosum lipase in AOT reverse micelles. In this study, it was assumed that when AOT reverse micelles contained PEG molecules, native and activated lipases contributed to the reaction according to their weight fraction in the system. The fractions of individual lipases and their specific activities were estimated by using kinetics parameters determined by previous kinetic models. The maximum specific activity of PEG-activated lipase appeared to be 2.7 times higher than that of native lipase. The predicted weighted-average activity agreed well with experimental data. The results showed that the previous kinetic models could be used to estimate the fraction of lipase activated by PEG molecules and their specific activity. Copyright © 2004 Society of Chemical Industry

The modification of AOT/water/isooctane reverse micellar system by various additives was undertaken to enhance the activity and stability of Chromobacterium viscosum lipase. Polypropylene glycols (PPG, MW 3 − ) of anionic surfactant AOT. Deactivation kinetic at 25 °C indicated that the C. viscosum lipase entrapped in AOT/PEG 400 reverse micelles was very stable, retaining over 75% of its initial activity after 60 days, whereas half-life time in simple AOT reverse micelles was 38 days.

Let A be a finitely generated variety of Heyting algebras and let SI(A) be the class of subdirectly irreducible algebras in A. We prove that A is dually equivalent to a category of functors from SI(A) into the category of Boolean spaces. The main tool is the theory of multisorted natural dualities.

The activity of Chromobacterium viscosum lipase (glycerol-ester hydrolase, EC 3.1.1.3) entrapped in AOT/isooctane reverse micelles was significantly increased by the addition of short chain polyethylene glycols (PEGs) or methoxypolyethylene glycols (MPEGs) for the hydrolysis of olive oil. To understand enzyme activity in the presence of PEG 400 or MPEG 550 molecules, a kinetic model was proposed. The validity of this model was verified by experimental data on the lipase-catalyzed hydrolysis of olive oil in AOT/isooctane reverse micellar systems, in which PEG 400 or MPEG 550 had been added. The large value of the equilibrium constant (kD) for enzyme activation indicated that the affinity between C viscosum lipase and PEG 400 or MPEG 550 molecules was very strong. The Michaelis constant (Km) predicted by the proposed model explained enzymatic reactions more exactly than that by the previously published model. Copyright © 2003 Society of Chemical Industry

The activity and stability of Chromobacterium viscosum lipase (glycerolester hydrolase, EC 3.1.1.3)-catalyzed olive oil hydrolysis in sodium bis (2-ethyl-l-hexyl)sulfosuccinate (AOT)/isooctane reverse micelles is increased appreciably when low molecular weight polyethylene glycol (PEG 400) is added to the reverse micelles. To understand the effect of PEG 400 on the phase behavior of the reverse micellar system, the phase diagram of AOT/ PEG 400/water/isooctane system was studied. The influences of relevant parameters on the catalytic activity in AOT/PEG 400 reverse micelles were investigated and compared with the results in the simple AOT reverse micelles. In the presence of PEG 400, the linear decreasing trend of the lipase activity with AOT concentration, which is observed in the simple AOT reverse micelles, disappeared. Enzyme entrapped in AOT/PEG reverse micelles was very stable, retaining75% of its initial activity after 60 d, whereas the half-life in simple AOT reverse micelles was 38 d. The kinetics parameter maximum velocity (Vmax) exhibiting the temperature dependence and the activation energy obtained by Arrhenius plot was suppressed significantly by the addition of PEG 400.

AOT/isooctane系逆相ミセル溶液にPEG400を添加した時のミセル内水相の構造変化を，FT-IRを用いて測定したO-H，C=O，S=O結合の伸縮振動スペクトルから調査し，AOT単独逆相ミセルの場合と比較した．逆相ミセル内水相は，trapped water，bound water，free waterで構成されている．AOT/PEG逆相ミセルではAOT単独逆相ミセルの場合に比べ，AOTのモル数当たりの水分子のモル数で表される含水率W0の増加と共にfree waterの割合は増加しており，ミセル界面近傍で形成されるbound waterの構造がPEG分子によって崩壊することが明らかとなった．更に，S=O結合赤外吸収スペクトルのピーク値のシフト，及びC=O結合の赤外吸収スペクトルから，W0> 6では水和したPEG分子によってAOT分子とミセル内水相の水分子間の相互作用が抑制されていることが明らかとなった．

The thermostability of Cromobacterium viscosum lipase (EC 3.1.1.3) entrapped in AOT (sodium bis-[2-ethylhexyl] sulfosuccinate) reverse micelles was increased by the addition of short-chain polyethylene glycol (PEG 400). Two different approaches were considered: (1) the determination of half-life time and (2) the mechanistic analysis of deactivation kinetics. The half-life of lipase entrapped in AOT/isooctane reverse micelles with PEG 400 at 60 degrees C was 28 h, ninefold higher than that in reverse micelles without PEG 400. The lipase entrapped in both reverse micellar systems followed a series-type deactivation mechanism involving two first-order steps. The deactivation constant for the first step at 60 degrees C in PEG containing reverse micelles was 0.055 h!1, 11-fold lower than that in reverse micelles without PEG, whereas it remained almost constant for the second step. The inactivation energy of the lipase entrapped in reverse micelles with and without PEG 400 was 88.12 and 21.97 kJ/mol, respectively.