1,494 research outputs found
On the origins of the compressive cochlear nonlinearity
No full textVarious simple mathematical models of the dynamics of the organ of Corti in the mammalian cochlea are analysed. The models are assessed against their ability to explain the compressive nonlinear response of the basilar membrane. The speci fic models considered are: phenomenological Hopf and cusp normal forms, a recently-proposed description combining active hair-bundle motility and somatic motility, a reduction thereof, and finally a new model highlighting the importance of the coupling between the nonlinear transduction current and somatic motility. The overall conclusion is that neither a Hopf bifurcation nor cusp bifurcation are necessary for realistic compressive nonlinearity. Moreover, two physiological models are discussed showing compressive nonlinearities similar to experimental observations without the need for tuning near any bifurcation
Rota–Baxter Operators on Cocommutative Weak Hopf Algebras
No full textIn this paper, we first introduce the concept of a Rota–Baxter operator on a cocommutative weak Hopf algebra H and give some examples. We then construct Rota–Baxter operators from the normalized integral, antipode, and target map of H. Moreover, we construct a new multiplication “∗” and an antipode SB from a Rota–Baxter operator B on H such that HB=(H,∗,η,Δ,ε,SB) becomes a new weak Hopf algebra. Finally, all Rota–Baxter operators on a weak Hopf algebra of a matrix algebra are given
The mitogenic potential of heparin-binding epidermal growth factor in the human endometrium is mediated by the epidermal growth factor receptor and is modulated by tumor necrosis factor-alpha
No full textHeparin-binding epidermal growth factor (HB-EGF), a member of the epidermal growth factor (EGF) family, is implicated in a variety of biological processes, including reproduction. Previous studies describe increased levels of HB-EGF in the human endometrium during the midsecretory stage of the menstrual cycle, suggesting a function for HB-EGF in implantation of the human blastocyst. Here we have investigated the expression and function of the soluble and transmembrane forms of HB-EGF in the human endometrium. We show that the expression of the transmembrane form of HB-EGF in the human endometrium is modulated according to the stage of the menstrual cycle. We present data demonstrating that both the soluble and transmembrane forms of HB-EGF induce DNA synthesis in human endometrial stromal cells. Furthermore, TNFalpha has a cooperative effect on HB-EGF, EGF, TGFalpha, and betacellulin-induced DNA synthesis in stromal cells, suggesting roles for the EGF family and TNFalpha in regeneration and maturation of human endometrium. Induction of DNA synthesis by HB-EGF and its modulation by TNFalpha in endometrial stromal cells are mediated by the EGF receptor and not the HB-EGF receptor ErbB4. Our data suggest key functions for HB-EGF, TNFalpha, and the EGF receptor in endometrial maturation, via autocrine/paracrine and juxtacrine pathways, in preparation for embryo implantation
On the Security of Non-Linear HB (NLHB) Protocol Against Passive Attack
No full textAs a variant of the HB authentication protocol for RFID systems, which relies on the complexity of decoding linear codes against passive attacks, Madhavan et al. presented Non-Linear HB(NLHB) protocol. In contrast to HB, NLHB relies on the complexity of decoding a class of non-linear codes to render the passive attacks proposed against HB ineffective. Based on the fact that there has been no passive solution for the problem of decoding a random non-linear code, the authors have claimed that NLHB’s security margin is very close to its key size. In this paper, we show that passive attacks against HB protocol can still be applicable to NLHB and this protocol does not provide the desired security margin. In our attack, we first linearize the non-linear part of NLHB to obtain a HB equivalent for NLHB, and then exploit the passive attack techniques proposed for the HB to evaluate the security margin of NLHB. The results show that although NLHB’s security margin is relatively higher than HB against similar passive attack techniques, it has been overestimated and, in contrary to what is claimed, NLHB is vulnerable to passive attacks against HB, especially when the noise vector in the protocol has a low weight
Hopf Bifurcation Control of Power System Nonlinear Dynamics via a Dynamic State Feedback Controller-Part I : Theory and Modeling
No full textThis two-part paper introduces a dynamic state feedback control law that guarantees the elimination of Hopf bifurcations (HB) before reaching the saddle-node bifurcations (SNB). Part I is devoted to the mathematical representation of the detailed system dynamics, investigation of HB and SNB theorems, and state feedback controller design. For purposes of dynamical analysis, the stable equilibria of the system is obtained. Then the control system is designed with the objective of preventing the voltage collapse before the SNB, such that the structural stability of the system is preserved in the stationary branch of the solutions. The controller aims to relocate Hopf bifurcations to the stationary branch of solutions located after SNB, eliminating the HB from normal operating region of the system. In order to evaluate the performance of the proposed controller, bifurcation analysis has been performed in Part II using single-machine and multi-machine test systems.</p
Determination of Hopf bifurcation sets of a chemicalreactors by two-parameter continuation method
No full textA two-parameter continuation method was developed and shown in the form of an example, allowingdetermination of Hopf bifurcation sets in a chemical reactor model. Exemplary calculations weremade for the continuous stirred tank reactor model (CSTR). The set of HB points limiting the rangeof oscillation in the reactor was determined. The results were confirmed on the bifurcation diagramof steady states and on time charts. The method is universal and can be used for various models ofchemical reactors
Legal regulation of prices in Tanzania : an examination of the Regulation of Prices Act 1973 as a tool of social change and development
No full textDrawing mainly from the Tazanian experience this study
attempts to review the principal issues in the legal regulation of
prices, by identifying both the general and specific importance
of law in this respect. The position I shall present is that
legal control is both necessary and desirable for the welfare
and social development of the people. The key issue is whether
the market-place will perform its function satisfactory: Will
it produce socially desirable results? If it will not, why will
it not? And will legal regulation help to do the job a little
better?
In an attempt to answer some of these questions,
first of all, outline the basic issues raised by the study in
the first Chapter. Then I examine the general case for price
controls - the theory about the controls, the motives and reasons
for their imposition and the manner in which they are effected
in different economic systems. This is done in Chapter Two. Relying
most on the available literature on the regulatory process, this
Chapter also looks at the relationship between law and economic
regulation and concludes that the effectiveness of law depends
on the existence of a conducive socio-economic environment. In
Chapter Three I describe the past record of price control laws
in Tanzania. I conclude that despite the failure in the past,
the controls still constitute an important policy instrument
in the transition to socialism. In Chapters Four and Five I describe
the manner in which the current regulations are implemented and
the problems encountered. I conclude that the operational performance
of the controls is constrained by internal and external influences on the economic and political life of the country. In the concluding
Chapter I assess the impact of the controls: Do the controls
work? Do people buy goods at the controlled prices? Why today
the controls are almost popularly accepted as worthwhile? I conclude
that while there may be no measurable economic gains derived
by consumers, the controls have a stabilising effect on the social
and political front. In the final section I argue that the
future success of the legislation depends on creating a correspondence
between the economic structures and the control system. What
makes the controls ineffective is not so much defects in the
law but the contradictions between the orientation of and functioning
of the economic system and the ideological commitment
On
No full textIn this paper, this author proved that always has
the integral solutions for Then we conjecture the equation always has the integral solutions
SOME NEWMAN-TYPE THEOREMS FOR MAPS FROM RIEMANNIAN-MANIFOLDS INTO MANIFOLDS
No full textMathematics, AppliedMathematicsSCI(E)1ARTICLE53-5911
SOME BORSUK-ULAM-TYPE THEOREMS FOR MAPS FROM RIEMANNIAN-MANIFOLDS INTO MANIFOLDS
No full textMathematics, AppliedMathematicsSCI(E)1ARTICLE61-6711
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