When a self - localized quasiparticle excitation propagates along a discrete one dimensional...

the protein folding problem has been around for a long time , with various incarnations . numerous proposals have been presented , to explain how the folding patterns emerge and advance . examples include nucleation - condensation , hydrophobic collapse and diffusion - collision controlled processes . more recently , a kink - based approach has been proposed and tested successfully using a coarse - grained force - field . at the same time , protein misfolding continues to be vigorously investigated . a misfolded protein can lead to serious complications , a misfolding transition is now widely accepted as the cause for diseases like type - ii diabetes , many forms of cancer , and dementia including alzheimer s . in the present article we investigate the phenomenon of _ barrier penetration _ as an example of those physical mechanisms that contribute to protein folding and misfolding transitions . for this we inquire what happens when a protein loop fragment becomes displaced from its native position . how does it find its way back to the native position ? the understanding of the dynamical processes involved should contribute to our comprehension of protein folding , including the reasons why and how a misfolding transition takes place . as a concrete example we consider an albumin - binding domain which is related to the protein g. this is a fairly generic -helical protein , the native state involves three helices which are separated by two short loops ; we use the protein data bank ( pdb ) entry code 1gab . it consists of 53 amino acids , the first loop is located between sites 19 - 24 and the second loop is located between sites 33 - 37 . the reason for choosing 1gab as our concrete example is , that the unres force field , on which our investigations are based , has been optimised for this particular protein . in our analysis of 1gab we first follow , to conclude that each of the two loops of 1gab are modeled by a single kink that solves a generalized discrete non

We investigate the phenomenon of barrier penetration in a protein - helical domain. We consider the kink - field as a generalized discrete non - linear force field for this domain, and show that it is a simple kinke - driven process.

when a self - localized quasiparticle excitation propagates along a discrete one dimensional lattice , it becomes subject to a dissipation that converts the kinetic energy into lattice vibrations . eventually the kinetic energy does no longer enable the excitation to cross over the minimum energy barrier between neighboring sites , and the excitation becomes localized within a lattice cell . in the case of a protein , the lattice structure consists of the c backbone . the self - localized quasip


Further imaging observations of a sample of radio sources in the north ecliptic cap are presented...

radio galaxies are at present the only high redshift galaxies which are not explicitly selected on the basis of high star formation rates , but which can nevertheless be found in reasonably large numbers . this makes them potentially very valuable for understanding the evolution of massive galaxies at early times . unfortunately , the strong correlation of the radio and uv emission in the most radio - luminous galaxies ( the `` alignment effect '' ; see , e.g. , best et al . 1997 and ridgway & stockton 1997 ) indicates that their photometric properties are probably dominated by the presence of an agn , at least at rest wavelengths , a deduction which was confirmed by spectroscopically for most 3c radio galaxies by hammer , lefvre & angonin ( 1993 ) . this makes defining and studying samples of radio sources selected at fainter flux density levels important , as , due to the correlation of radio luminosity with the optical / uv luminosity of the agn ( e.g. willott et al . 1999 ) , such objects should have only a very small fraction of their light produced by the agn . in two previous papers ( lacy , rawlings & warner 1992 ; lacy et al . 1993 ; hereafter papers i and ii ) , we defined and presented radio and optical imaging data for a sample of radio sources selected from the 38-mhz survey of rees ( 1990 ) in the region of the north ecliptic cap ( nec ) . in a companion paper ( lacy et al . 1999b ; hereafter paper iv ) we present optical spectroscopy of this sample , along with that of a sample selected at 151mhz with a comparable flux limit and in the same region of sky ( the 7c - iii sample , lacy et al . 1999c ) and which therefore has most objects in common with this sample . we have already discussed the outcome of high - resolution optical observations of a sub - sample of objects from the 7c - iii sample which show that the radio optical `` alignment effect '' in the 7c - iii sample is weak , but probably present , even at wavelengths longward of 4000(lacy et a

We present optical spectroscopy of the sample of radio sources selected from the 38-mhz survey of rees ( 1990 ) in the region of the north ecliptic cap ( nec ). We show that the sample has a very small fraction of its light produced by the agn, and that it is likely to be a large fraction of the luminosity of the source. This suggests that the presence of an aggn at fainter flux density levels is important for understanding the evolution of massive galaxies at early times.

further imaging observations of a sample of radio sources in the north ecliptic cap are presented and a number of new identifications are made . using redshifts from spectroscopic data presented in a companion paper ( lacy et al . 1999b ) , the photometric properties of the galaxies in the sample are discussed . it is shown that : ( 1 ) out to at least radio galaxies are good standard candles irrespective of radio luminosity ; ( 2 ) for a large fraction of the sample have magnitudes and colours


Mechanical ventilation is used for patients with a variety of lung diseases

biological systems are inherently adaptive and have evolved to survive stressors and randomness . beyond being robust to stressors , they are in fact evolutionarily designed to ` gain ' from them . this property of systems has been referred to as ` antifragility ' . antifragile systems benefit from stressors or noise . here , by ` stressors ' one refers to unfavorable abiotic changes in external milieu such as temperature , ph , pressure etc . a system s reaction to any external stressor or stimuli could be enumerated through a measurable property that reflects gain or loss in response to the stressor . it has been argued that a system having convex response would benefit from addition of noise . many of the biological systems have convex responses due to evolutionary selection that they have undergone . modeling the nature of such system responses would help in better understanding of design principles of biological systems that help them to thrive under stressful circumstances . human engineered systems are designed to cope with stable signals . an electrical system is designed assuming unvarying electrical signal and structural systems are designed for absence of severe seismic disturbances . thus , signal variability reflects ` noise ' and is harmful to the system . classically physiological systems are thought to be designed to reduce variability and to attain homeostasis . in contrast , signals of a wide variety of physiological systems , such as human heartbeat , brain s electrical activity etc . , fluctuate in a complex manner . in fact , a defining feature of a living organic system is adaptability , the capacity to respond to unpredictable stimuli . a lung is a physiological system that serves towards respiration , critical for oxidative processes in organisms . human breathing is driven by pressure generated through spontaneous muscular action . the lungs are ventilated in response to this pressure . the lung volume representing the normal volume of air d

We study the effects of stress on a system s response to a variety of stimuli. We show that the respiratory rate is dependent on the amount of pressure generated by the system. This effect is characterized by a pronounced increase in the volume of the lung, which is a function of the pressure. The resulting decrease in the size of the lungs is attributed to the presence of a large number of different stimuli that are present in the system and a small number of other factors.

mechanical ventilation is used for patients with a variety of lung diseases . traditionally , ventilators have been designed to monotonously deliver equal sized breaths . while it may seem intuitive that lungs may benefit from unvarying and stable ventilation pressure strategy , recently it has been reported that variable lung ventilation is advantageous . in this study , we analyze the mean tidal volume in response to different ` variable ventilation pressure ' strategies . we found that unifor


We present a brownian dynamics model of driven polymer translocation , in which non - equilibrium...

the transport of a polymer across a nanopore is vital to many biological processes , such as dna and rna translocation through nuclear pores , protein transport across membrane channels and virus injection . due to various potential technological applications such as rapid dna sequencing , gene therapy and controlled drug delivery , polymer translocation has received considerable experimental and theoretical interest . of particular technological interest is the case of driven translocation , where the process is facilitated by an external driving force . the key theoretical issue here is to find a unifying physical description that yields the correct dynamical behavior , e.g. , the dependence of the translocation time on the chain length . experiments and numerical simulations have indicated that . however , numerous different values of have been observed , suggesting explicit dependence on the various physical parameters ( cf . ref . for a recent review ) . several theories of driven polymer translocation have emerged , some claiming agreement with the experimental or numerical results within a certain subset of the physical parameter space . however , to date no single theory has been able to capture the wide range of observed values of , nor quantitatively explain the reason for their dependence on the system s parameters . therefore , the need for a unifying theory of driven translocation remains . in refs . , polymer translocation was described as a one - dimensional barrier crossing problem of the translocation coordinate ( the length of the subchain on the _ trans _ side ) . here , the chain starts from the _ cis _ side with one end inside the pore ( ) and is considered as translocated once , with the segment length . the free - energy due to chain entropy and the chemical potential difference is + {a}.$ ] here is the surface exponent ( for an ideal chain , self - avoiding chain in 2d and 3d , respectively ) , and is the thermal energy . from , the brownian

We present a new theory of driven polymer translocation, which is based on the one - dimensional barrier crossing problem of the chain length. The system is described as a one -dimensional barrier cross problem of a chain length with one end inside the pore. In this paper, we show that the chain is driven by an external driving force, and that the free - energy due to chain entropy and the chemical potential difference is + a$ ].

we present a brownian dynamics model of driven polymer translocation , in which non - equilibrium memory effects arising from tension propagation ( tp ) along the _ cis _ side subchain are incorporated as a time - dependent friction . to solve the effective friction , we develop a finite chain length tp formalism , based on the idea suggested by sakaue [ sakaue , pre 76 , 021803 ( 2007 ) ] . we validate the model by numerical comparisons with high - accuracy molecular dynamics simulations , show


We study the bond percolation problem in random graphs of weighted vertices , where each vertex has...

in the last few years graph theoretic approach has been of great value to characterize complex systems found in social , informational and biological areas . here , a complex system is represented as a graph or network whose vertices and edges stand for its constituents and interactions . a simplest model for such is the random graph model proposed by erds and rnyi ( er ) . in the er model , number of vertices are present from the beginning and edges are added one by one in the system , connecting pairs of vertices selected randomly . due to the randomness , the distribution of the number of edges incident on each vertex , called the degree distribution , is poissonian . however , many real - world networks such as the world - wide web , the internet , the coauthorship , the protein interaction networks and so on display power - law behaviors in the degree distribution . such networks are called scale - free ( sf ) networks . thanks to recent extensive studies of sf networks , various properties of sf network structures have been uncovered . there have been a few attempts to describe scale - free networks in the framework of equilibrium statistical physics , even though the number of vertices grows with time in many real - world networks . in this approach , various mathematical tools developed in equilibrium statistical physics may be used to understand network structures . to proceed , one needs to define equilibrium network ensembles with appropriate weights , where one graph corresponds to one state of the ensemble . in a canonical ensemble , the number of edges is fixed : given a degree distribution , , the mean degree is obtained . then the number of edges obtained through the relation , , can be fixed . a degree sequence specifies the number of vertices with degree as . a grandcanonical ensemble can be also defined , where the number of edges is also a fluctuating variable while keeping the sf nature of the degree distributions . the grandcanonical ensemble f

We study the sf network structure in the framework of equilibrium statistical physics. We show that the number of edges is also a fluctuating variable while keeping the symmetric nature of the degree distributions.

we study the bond percolation problem in random graphs of weighted vertices , where each vertex has a prescribed weight and an edge can connect vertices and with rate . the problem is solved by the limit of the -state potts model with inhomogeneous interactions for all pairs of spins . we apply this approach to the static model having so that the resulting graph is scale - free with the degree exponent . the number of loops as well as the giant cluster size and the mean cluster size are obtained


We investigate the electronic state of a coo plane in the layered cobalt oxides nacoo using the 11...

the discovery of superconductivity in the layered cobalt oxide nacoyho has stimulated further interest in the electronic states of the mother compound nacoo . the specific features of the system are the geometrical fluctuation of the coo plane which consists of a triangular lattice of co atoms , and the orbital degeneracy of bands of co electrons . the electron filling in the coo plane is controlled by changing the na content : the hole concentration of co bands is given by . for , nacoo is a normal paramagnetic metal , while , for , an anomalous behavior is observed : the magnetic susceptibility is curie - weiss like although the resistivity is metallic , the electronic specific heat coefficient is large and increases with , the thermopower is unusually large . for , a weak magnetic order is observed below 20k , where the ferromagnetic ordered coo layers couple antiferromagnetically with each other . furthermore , nacoo exhibits a remarkable successive phase transition at k and k : the in - plane antiferromagnetic order is realized below and the system becomes insulator below . from the nmr and the neutron measurements , yokoi _ et . _ have proposed the magnetic structure of nacoo , where chains of co with larger staggered moment and co with smaller moment exist alternatively within the coo plane . the charge ordering of the co sites into chains of co and co is closely related to the ordered pattern of na ions which form one - dimensional chains below room temperature . in spite of the intense effort devoted in the last few years , the origin of metal - insulator transition at is still an open question . the purpose of this paper is to investigate the electronic state of the coo plane including the successive phase transition of nacoo , particularly focused on the effect of the one - dimensional na order on the antiferromagnetism . for this purpose , we take into account of an effective one - dimensional potential on the coo plane due to the effect of the na order

We investigate the electronic state of the layered cobalt oxide nacoyho, including the successive phase transition. We consider the effect of the one - dimensional na order on the antiferromagnetic order and the magnetic susceptibility of the system.

we investigate the electronic state of a coo plane in the layered cobalt oxides nacoo using the 11 band d - p model on a two - dimensional triangular lattice , where the tight - binding parameters are determined so as to fit the lda band structure . effects of the coulomb interaction at a co site : the intra- and inter - orbital direct terms and , the exchange coupling and the pair - transfer , are treated within the hartree - fock approximation . we also consider the effect of the na order at ,


Stability and attractor property of free - floating axisymmetric magnetic bubbles in high -...

we show that compact non - singular axisymmetric equilibrium magnetic field configurations are attractors ( more precisely intermediate asymptotics ) in a weakly dissipative plasma . this means that some initial magnetic field configurations evolve into solitary magnetic bubbles . because of the attractor property , such free - floating solitary magnetic bubbles should exist in nature ( see braithwaite 2010 and references therein ) . first consider magnetic equilibria of ideally conducting incompressible plasmas . the magnetic field will be in equilibrium if the magnetic force is balanced by the pressure gradient : it turns out , that due to topological obstacles ( arnold 1986 ) , generic magnetic equilibria , that is generic solutions of eq.([equi ] ) , contain singular current layers ( gruzinov 2009 ) . if the plasma electric conductivity is finite , but still very high , the magnetic diffusivity will disperse the singular current layers by the reconnection process , without dispersing the entire magnetic field configuration . this is the intermediate - asymptotic stage we are interested in . during the intermediate - asymptotic stage , the magnetic equilibrium configuration should be non - singular . ideally , we want to find all compact non - singular magnetic equilibria . we think we have a full solution of this problem in two dimensions ( 3 ) . in 2d , the only compact non - singular equilibrium is a circular - symmetric magnetic bubble . in 3d , there is a class of non - singular equilibrium configurations compact axisymmetric magnetic bubbles ( 4 ) . the non - singular axisymmetric equilibrium bubbles are attractors ( 5 ) . but unlike the 2d case , we do not know if these bubbles are the only non - singular compact attractors . we study magnetic equilibria using the relaxation method ( e.g. gruzinov 2009 ) . we put an arbitrary compact magnetic field into high - viscosity small - magnetic - diffusivity plasma , and let the plasma move under the resulting mag

We study the non - singular axisymmetric equilibrium magnetic field configurations in a weakly dissipative plasma. We show that the compact non - single axisymmetry is attractors ( more precisely intermediate asymptotic ) in. This means that some initial magnetic field Configurations evolve into solitary magnetic bubbles.

stability and attractor property of free - floating axisymmetric magnetic bubbles in high - conductivity plasmas is ( tentatively , numerically ) demonstrated . the existence of compact non - singular axisymmetric magnetic equilibria is proved . being attractors , the solitary magnetic bubbles should exist in nature .


We modify the concept of quantum strategic game to make it useful for extensive form games

over the period of twelve years of research on quantum games , the idea of quantum strategic game has been well established . from mathematical point of view , the quantum information approach to a game is described by the four - tuple : the hilbert space is the place of the game and the sets of unitary operators play the role of strategy sets for the first and the second player , respectively . given a unit vector ( _ the initial state _ ) , the players each choose a unitary operator changing the vector into the vector ( _ the final state _ ) . the last components are the functionals for . they imitate payoff functions for the players assigning a real number to the final state . it turns out that the four tuple ( [ fourtuple ] ) generalizes playing a classical game . the two well - known ways based on the framework ( [ fourtuple ] ) : the eisert - wilkens - lewenstein ( ewl ) scheme and the marinatto - weber ( mw ) scheme show that a game can be successfully written in the form ( [ fourtuple ] ) : it is possible to set each of the four components , so that a game and the corresponding game defined by the four - tuple ( [ fourtuple ] ) are the same with respect to a game - theoretic analysis . another key feature is that the protocol ( [ fourtuple ] ) allows to achieve results unavailable in the game played classically ( see , for example , and ) . in our paper we are going to deal with extensive games in quantum domain . in spite of quite many researches connected with this issue ( for instance , concerning quantum stackelberg duopoly and ) , there is no generally accepted framework for playing quantum extensive games by now . interestingly , we have shown in that ( [ fourtuple ] ) may indeed be useful for extensive games with imperfect information . in this paper , we extend our previous idea . we prove that the slight modification of allows to obtain normal representation of extensive games in the quantum domain . definitions in the preliminaries are based on . t

We prove that the four - tuple ( [ fourtuples ] ) can be used to play extensive games in the quantum domain. We show that the small modification of the framework allows to obtain normal representation of extensive games with imperfect information.

we modify the concept of quantum strategic game to make it useful for extensive form games . we prove that our modification allows to consider the normal representation of any finite extensive game using the fundamental concepts of quantum information . the selten s horse game and the general form of two - stage extensive game with perfect information are studied to illustrate a potential application of our idea . in both examples we use eisert - wilkens - lewenstein approach as well as marinatt


Assuming lorentz symmetry is broken by some fixed vector background , we study the spinor...

the breaking of lorentz symmetry is an extensively studied topic . although no departure from lorentz invariance has yet been detected experimentally , there is no reason to believe that lorentz invariance would be intact at all energies . as a matter of fact , there are reasons to suspect its exactness in the context of string theory . for example , the potential instability of string vacuum would induce spontaneous breakdown of lorentz symmetry . also , high - energy field theories constructed on a moyal space , viewed as low - energy effective theories from open string theory with a constant ns - ns field , explicitly spoil lorentz invariance . one direction in the study of lorentz violation is to regard lorentz symmetry breaking as a possible extension of the standard model in particle physics . the first work in this context is the investigation of the carroll - field - jackiw term , which has inspired numbers of studies in recent years . without the criterion of lorentz symmetry , one may construct new additive terms to the minimal standard model . note that since invariance is necessary but not sufficient for lorentz invariance of an interacting quantum field theory , lorentz violating ( lv ) terms can be either even or odd . lv terms of renormalizable dimensions have been systematically constructed in , known as the standard model extension , and many related issues have been discussed . however , experimental data put very stringent constraints on the renormalizable lv terms and indicate that they must be extremely small . to avoid the subtle fine - tuning problem , we assume that the symmetry of the underlying theory prohibits the generation of the renormalizable lv operators and explore the nonrenormalizable lv operators in this paper . renormalizability was considered to be an axiom when constructing the standard model . quantum corrections to a renormalizable theory will generate uv divergences only to operators whose mass dimensions are less than five

We study the lorentz violation of a standard model in particle physics by using the carroll - field - jackiw term. We find that the renormalizable lv terms are not even or odd, and that they can be either even or even. The nonrenormalisable lorenz violating ( l ) operators are also studied.

assuming lorentz symmetry is broken by some fixed vector background , we study the spinor electrodynamics modified by two dimension - five lorentz - violating interactions between fermions and photons . the effective polarization and magnetization are identified from the modified maxwell equations , and the theoretical consequences are investigated . we also compute the corrections to the relativistic energy levels of hydrogen atom induced by these lorentz - violating operators in the absence an


We have used the iram plateau de bure millimeter interferometer and the ukirt 15 m imager...

it has been established that every massive , local spheroid harbours a supermassive black hole ( smbh ) in its centre whose mass is proportional to that of its host ( e.g. ; ) . this suggests that the black holes ( bhs ) and their surrounding galaxies were formed synchronously . this hypothesis has found support from hydrodynamical simulations of galaxy formation , which use feedback from winds and outflows from active galactic nuclei ( agn ) to link the growth of the smbh to that of its host ( e.g. ; ; ) . thus these models support a picture , first presented by , where a starburst - dominated ultra - luminous infrared galaxy ( ulirg ) , arising from a merger , evolves first into an obscured qso and then into an unobscured qso , before finally becoming a passive spheroid . the high - redshift population of ulirgs in this proposed evolutionary cycle are the submillimetre ( submm ) galaxies ( smgs ; ; ; ) . these systems have ulirg - like bolometric luminosities , l ( ; ) , and they have many of the properties expected for gas - rich mergers ( ; ) . this population evolves rapidly out to a peak at , crudely matching the evolution of qsos and providing additional circumstantial evidence for a link between smbh growth and spheroids . two further results have shed light on the evolutionary link between smgs and qsos . firstly , a modest fraction of optically luminous qsos at are detected in the submm / mm ( % ; ) showing that the qso- and smg - phases do not overlap significantly , given the lifetime estimates of the two populations ( qsos make up % of flux - limited samples of smgs ; ) . but when a qso _ is _ detected in the submm / mm then it could to be in the transition phase from an smg to an unobscured qso , making its properties a powerful probe of the evolutionary cycle ( e.g. ; ) . secondly , the evolutionary state of the smbhs within smgs can also be judged using the 2-ms _ chandra _ deep field north observations to derive accurate agn luminosities and hence l

We present a new study of the evolution of submillimetre ( ) galaxies in the presence of a starburst - dominated supermassive black hole ( smbh ). This is a model for galaxy formation that uses feedback from winds and outflows from active galactic nuclei to link the growth of the spheroids to that of their host. We show that the qso phase evolves rapidly out to a peak at, roughly matching the evolution in s.

we have used the iram plateau de bure millimeter interferometer and the ukirt 15 m imager spectrometer ( uist ) to test the connection between the major phases of spheroid growth and nuclear accretion by mapping co emission in nine submillimetre - detected qsos at .6 with black hole ( bh ) masses derived from near - infrared spectroscopy . when combined with one qso obtained from the literature , we present sensitive co(32 ) or co(21 ) observations of 10 submillimetre - detected qsos selected at


Computer simulation of the hopping charge transport in disordered organic materials has been...

hopping transport in disordered organic materials has been extensively studied for the case of low density of carriers , but our understanding of charge transport for the case of high carrier density is not adequate ; theoretical studies of the effect of carrier density are scarce . high density of carriers could affect drift mobility in opposite ways . small fraction of carriers could occupy deep states , thus providing a possibility for remaining carriers to avoid trapping and acquire much higher mobility . at the same time , charge - charge interactions could provide an additional energetic disorder in the material . this is indeed the case for the simplest model where all charges except one are immovable . in this case , the greater is the density of static charges ( i.e. energetic disorder ) , the smaller is the mobility . usually , in theoretical studies the mean field approximation has been used and charge - charge interaction has been totally neglected . this means that these studies dealt only with the effect of filling of deep states : it is assumed that the effects of interaction could be later effectively included via the mobility dependence on the mean local electric field , which in turn is connected to the mean local charge density by the poisson equation where is a dielectric constant of the material . this line of reasoning totally neglects dynamic correlations . in addition , quite frequently true quasi - equilibrium mobility is formed by the averaging over large domains of the disordered material ( see , for example , ref . ) . in this situation the very conception of a local ( but uniform in space ) mobility is invalid . for this reason in this paper we describe a direct dynamic simulation of hopping monopolar transport of _ interacting _ carriers . for the model of interacting carriers the total site energy of a carrier is a sum of a static random contribution due to the static intrinsic energetic disorder and fluctuating contribution due to the

We study the dynamic simulation of hopping monopolar transport in disordered organic materials with a large density of carriers. The total site energy of a carrier is a sum of a static random contribution due to the static intrinsic energetic disorder and fluctuating contribution due the static dynamic disorder. For the model of interacting carriers the total Site energy is.

computer simulation of the hopping charge transport in disordered organic materials has been carried out explicitly taking into account charge - charge interactions . this approach provides a possibility to take into account dynamic correlations that are neglected by more traditional approaches like mean field theory . it was found that the effect of interaction is no less significant than the usually considered effect of filling of deep states by non - interacting carriers . it was found too th


An ensemble of random unistochastic ( orthostochastic ) matrices is defined by taking squared...

consider a square matrix of size containing non - negative entries . it is called _ stochastic _ if each row sums to unity ( for ) ( for information about properties of such matrices consult ) . if , additionally , each of its columns sums to unity , i.e. , for , it is called _ bistochastic _ ( or _ doubly stochastic _ ) . bistochastic matrices emerge in several physical problems . they are used in the theory of majorization , angular momentum , in transfer problems , investigations of the frobenius - perron operator , and in characterization of completely positive maps acting in the space of density matrices . we shall denote by ( resp . ) the sets of stochastic ( resp . bistochastic ) matrices of size . a matrix is called _ orthostochastic _ , if there exists an orthogonal matrix , such that for . analogously , a matrix is called _ unistochastic _ ( _ unitary - stochastic _ ) , if there exists a unitary matrix , such that for . due to unitarity ( orthogonality ) condition every unistochastic ( orthostochastic ) matrix is bistochastic . these four sets of nonnegative matrices are related by the following inclusion : , where and represent the sets of unistochastic ( orthostochastic ) matrices . for all three inclusions are proper . unistochastic matrices appear in analysis of models describing the time evolution in quantum graphs and in description of non - unitary transformations of density matrices . moreover , the theory of majorization and unistochastic matrices plays a crucial role in recent research on local manipulations with pure states entanglement or in characterizing the interaction costs of non local quantum gates . in this work we analyse the structure of the set of bistochastic ( unistochastic ) matrices of a fixed size and investigate the support of their spectra . knowledge of any constraints for the localisation of the eigenvalues of such a matrix is of a direct physical importance , since the moduli of the largest eigenvalues determine the rate of

We study the structure of a set of bistochastic ( unistochastic ) matrices of a fixed size and investigate the support of their spectra.

an ensemble of random unistochastic ( orthostochastic ) matrices is defined by taking squared moduli of elements of random unitary ( orthogonal ) matrices distributed according to the haar measure on ( or , respectively ) . an ensemble of symmetric unistochastic matrices is obtained with use of unitary symmetric matrices pertaining to the circular orthogonal ensemble . we study the distribution of complex eigenvalues of bistochastic , unistochastic and orthostochastic matrices in the complex pla


We present the results of a high - resolution imaging survey for brown dwarf binaries in two open...

brown dwarfs ( bds ) are very low - mass objects that do not stabilize on the hydrogen - burning main sequence because they develope degenerate cores . they are akin to giant planets in that their luminosity and temperature drop continuously with time , and ultimately they become extremely cool and faint . the borderline between stars and bds has been known for 40 years to be at about 0.08 solar mass ( m ) for solar metallicity ( hayashi & nakano 1963 ; kumar 1963 ) . recent calculations yield a substellar limit at 0.072 m ( e.g. baraffe et al . 1998 ) . for many years bds eluded firm detection , but since 1995 ( nakajima et al . 1995 ; rebolo , zapatero osorio , & martn 1995 ) there has been a pletora of discoveries . the evidence for bds is based on observations of lithium , luminosity and surface temperatures of faint dwarfs , as well as astrometric and radial velocities of main sequence stars . dynamical measurements of bd masses are becoming available with the study of nearby binaries where both components are substellar ( martn et al . 2000b ; lane et al . 2001 ) . recent censuses of bds in young open clusters indicate that they are numerous ( bjar et al . 2001 ; moraux et al . 2003 ) . with increasing age , bds cool down and reach very faint luminosities , becoming indeed very difficult to detect . young stellar associations and open clusters have provided a gold mine for bd searches because these objects are still in the early phase of gravitational contraction . hence , they are brighter and warmer than older bds . several processes of bd formation have been studied in some detail in the last few years . they can be divided in two main groups : ( 1 ) failed star - formation model : bds are ejected from unstable multiple systems during the collapse and fragmentation of a turbulent molecular cloud ( reipurth & clarke 2001 , 2003 ; sterzik & durisen 2003 ) ; ( 2 ) small star - formation model : bds result from the collapse of small cores of substellar mass in

We present a new method for the detection of brown dwarfs in young open clusters. We use a simple, non - invasive technique to detect brown dwarf masses and luminosities in the presence of a single star. The method is based on a spectroscopic analysis of the stellar surface temperature and luminescence of the object. It is shown that the observed luminosity and temperature are consistent with the bds, but they are not consistent with their radial velocity.

we present the results of a high - resolution imaging survey for brown dwarf binaries in two open clusters . the observations were carried out with the wide field planetary camera 2 onboard the hubble space telescope . our sample consists of 8 brown dwarf candidates in persei and 25 brown dwarf candidates in the pleiades . we have resolved 4 binaries in the pleiades with separations in the range 0.0940.058 , corresponding to projected separations between 11.7 au and 7.2 au . no binaries were fou


The standard model of cosmology is investigated using time - dependent cosmological constant and...

the astrophysical observations of supernovae of type ia give a convincing evidence of a universe undergoing an accelerated phase of its expansion history ; rather than going to deceleration as was expected theoretically . similar conclusion has been deduced from the observations of anisotropies in cosmic microwave background by the wmap which favors a low density , spatially flat ( ) universe filled with an exotic vacuum energy containing the maximum portion of the total energy density , . this mysterious dark energy is represented by a barotropic equation of state ( eos ) , where and is the pressure and the energy density of dark energy , with . if , it is called ` cosmological constant ' , is dubbed ` quintessence ' , while it is called ` phantom energy ' if . all these candidates have some fundamental problems : the former one presents discrepancy of orders of magnitude between theoretical and empirical results , while quintessence requires fine tuning of cosmological parameters for a suitable choice of the potential function . also the phantom energy yields eccentric predictions like ` big rip ' and ripping apart of gravitationally bound objects . moreover , the variations in suggest that there is no consensus on the actual eos of dark energy and one can only deal with the upper and lower bounds on . although the dark energy is generically considered to be a perfect fluid yet it need not to be perfect if it experiences perturbations . moreover , the dark energy also may not be completely ` dark ' especially if it gets coupled with matter and energy exchange takes place ; consequently the matter evolution becomes modified . it is now obvious that this sudden transition to acceleration from the earlier deceleration phase is rather recent with the corresponding redshift . it has been proposed that the standard model of cosmology may not be sufficient to explain this exotic phenomenon and hence significant modifications are proposed like a modified friedmann equatio

We present a new model of cosmology which is based on the equatio of dark energy and its relation to the mass density. It is shown that the corresponding redshift is not sufficient to explain this exotic phenomenon.

the standard model of cosmology is investigated using time - dependent cosmological constant and newton gravitational constant . the total energy content is described by the modified chaplygin gas equation of state . it is found that the time - dependent constants coupled with the modified chaplygin gas interpolate between the earlier matter to the later dark energy dominated phase of the universe . we also achieve a convergence of the parameter , almost at the present time . thus our model fair


We discuss various scattering properties of non - topological solitons , q - balls , on potential...

motivated by our earlier work on the scattering of topological solitons on potential obstructions in a class of models [ 1,2 ] we have decided to look at the generality of these results . to do this we have decided to investigate the scattering properties of non - topological solitons so in this paper we look at the scattering of q - balls on various potential obstructions . first we recall that q - balls are non - topological soliton fields , first introduced by s. coleman in [ 3 ] . they arise in some classes of self - interacting complex scalar fields . unlike topological solitons , whose stability is ensured by the presence of a conserved topological charge , q - balls carry a conserved noether charge associated with the global symmetry . this conserved but non - topological charge stabilises the q - balls . also , q - balls have a time - dependent rotating phase and the conserved noether charge is related to the velocity of the change of this phase . these features result in a much more complicated scattering properties of these solitons , leading to such phenomena as , for example , the charge fission during the scattering process . in this paper we investigate the q - ball dynamics in and dimensions , mainly when the q - balls are scattered on various obstructions in the form of potential barriers or holes . first we discuss the conditions of the stability of the q - balls . then we report the results of our numerical simulations which have revealed that q - balls behave like topological solitons only for the values of the parameters of the theory that guarantee this stability throughout the scattering . when this condition is satisfied the dynamics of the scattering on barriers and holes in dimensions is similar to what was seen for topological solitons [ 1,2 ] , _ ie _ very little radiation is given off during the scattering . the scattering on barriers results in transmission or reflection , _ ie _ very much like that of a small particles . in the scatteri

We investigate the scattering of q - balls on potential obstructions in and dimensions, mainly when the q balls are scattered on various obstructions. First we discuss the conditions of the stability of the solitons, then we report the results of our numerical simulations which have revealed that q Balls behave like topological sOLITONS only for the values of the parameters of the theory that guarantee this stability throughout the scatterING process.

we discuss various scattering properties of non - topological solitons , q - balls , on potential obstructions in and dimensions . these obstructions , barriers and holes , are inserted into the potential of the theory via the coupling parameter , , that is effective only in a certain region of space . when the obstruction is a barrier and when the obstruction is a hole . the dynamics of q - balls on such obstructions in dimensions is shown to be very similar to that of topological solitons prov


We consider a general d - wave superconducting gap function in the presence of coexisting...

the interplay and competition between antiferromagnetism ( afm ) and superconductivity ( sc ) is a long studied subject both experimentally and theoretically . there are now several heavy fermion compounds showing clear experimental evidence of the microscopically homogeneous coexistence of afm and sc correlations . however , the direct consequences of the coexistence of afm and sc has not yet been clearly resolved . recent in- nqr studies of cerhin and cein also revealed that there is a coexistence region of afm and sc around the critical pressures of 1.6 gpa and 2.43 gpa , respectively . apart from confirming the coexistence of afm and sc in this region of pressure , an interesting observation is that the nuclear spin - lattice relaxation rate displays the linear temperature dependence t at low temperatures ( up to 0.3 t for cerhin ) , followed by the t behavior below the superconducting transition temperature t . the latter behavior is an indication of the lines of nodes of the anisotropic sc state . the standard explanation of the t - linear temperature dependence of at low temperatures is the impurity effect in an unconventional sc with lines of nodes . however , this impurity explanation has difficulties in the case of cerhin ; the low temperature t - linear is only observed in the afm and sc coexistence region at 1.6 gpa , and once the afm order disappears by increasing pressure to 2.1 gpa , exhibits a t behavior for the entire measured temperatures below t . similar pressure dependence of has also been observed in ge - substituted cecusi . another afm heavy fermion superconductor urusi also shows the low temperature t - linear behavior in . in the case of updal , the situation is somewhat different ; a more recent nmr experiment indicates that the t - linear behavior observed in earlier experiments disappears with purer samples . putting together these observations we think that the interplay of the afm and sc , together with some sort of impurity effects ,

We present a new study of the interplay between antiferromagnetism and superconductivity in afm heavy fermion compounds. The results are consistent with previous studies of cerhin and cein, which show that the interplayer of antiferROMagnets is strongly dependent on the spin - lattice relaxation rate.

we consider a general d - wave superconducting gap function in the presence of coexisting antiferromagnetic ( afm ) long - rang order . we find that the d - wave order parameter develops additional nodes without lowering the symmetry of the state due to the interplay of the superconducting and afm correlations . this afm correlated d - wave gap has a small gap structure inside the generic d - wave gap . as a result of this additional structure it shows a quite different response to impurities co


Spectral fitting of the radio through hard x - ray emission of bl lac objects has previously been...

after the detection of 6 high - frequency peaked bl lac objects ( hbls ) with ground - based air erenkov telescope facilities , the field of extragalactic gev tev astronomy is currently one of the most rapidly expanding research areas in astrophysics . the steadily improving flux sensitivities of the new generation of air erenkov telescope arrays and their decreasing energy thresholds , provides a growing potential to extend their extragalactic - source list towards intermediate and even low - frequency peaked bl lac objects ( lbls ) with lower peak frequencies in their broadband spectral energy distributions ( seds ) . detection of such objects at energies 100 gev might provide an opportunity to probe the intrinsic high - energy cutoff of their seds since at those energies , absorption due to the intergalactic infrared background is still expected to be negligible at redshifts of . theoretical predictions of the high - energy emission of bl lac objects on the basis of their emission at lower frequencies are essential for careful planning of future observations by ground - based vhe -ray observatories . such studies have generally been restricted to considerations of the observed broadband spectral properties of potential candidate sources and have mostly been based on non - simultaneous spectral measurements alone . in this paper , we point out that such considerations can have very large uncertainties and ambiguities with respect to the predicted vhe emission . the importance and potential scientific return of including detailed variability information in the modeling of hbls has been pointed out by who have shown the wide variety of correlated x - ray and vhe -ray variability patterns which can result in time - dependent synchrotron - self - compton models for blazars . in particular , they have pointed out that combined x - ray spectral and variability information may be sufficient to predict the level of intrinsic tev emission in hbls , even if no direct measur

We present a new method for the prediction of the intrinsic tev emission in high - frequency peaked bl lac objects ( hbls ) with ground - based air erenkov telescope facilities. This technique is based on the combination of x -ray and variability information which can be used to predict the emission level of h -bl objects at low frequencies. We show that such an approach can be applied to the observation of bbl - lattice objects at energies 100 gev.

spectral fitting of the radio through hard x - ray emission of bl lac objects has previously been used to predict their level of high - energy ( gev tev ) emission . in this paper , we point out that such spectral fitting can have very large uncertainties with respect to predictions of the vhe emission , in particular if no reliable , contemporaneous measurement of the gev flux is available and the peak ( flux and frequency ) of the synchrotron component is not very precisely known . this is dem


We investigate the phenomenon of extinction of a long - lived self - regulating stochastic...

extinction of an isolated stochastic population after maintaining a long - lived state is a dramatic phenomenon . it occurs , even in the absence of environmental variations , because of an unusual chain of random events when population losses dominate over gains . population extinction risk is a key negative factor in viability of small populations , whereas extinction of a disease following an epidemic outburst is of course favorable . the possibility and consequences of extinction of biologically important components , regulated by chemical reactions in living cells , have also attracted interest . as stochastic population dynamics are usually far from equilibrium , and no general methods of evaluating large fluctuations are available , they are of much interest to physics . this work deals with an isolated single - species population undergoing a set of gain - loss processes . we will assume that the population is well mixed , so that spatial degrees of freedom are irrelevant . at the level of the _ deterministic rate equation _ ( henceforth _ rate equation _ ) , which describes the time history of the mean population size and ignores fluctuations , flows to an attracting fixed point , where the gain and loss processes balance each other . the actual stochastic population , however , behaves differently and ultimately becomes extinct . this is because , in the absence of influx of new individuals , the empty state is _ absorbing _ : the probability of exiting from it is zero . although extinction ( and fluctuations in general ) are beyond its scope , the rate equation is a convenient starting point of our analysis . for an isolated single - species population the rate equation can be written as where is a smooth function determined by the specific gain - loss processes , see below . for generic gain - loss processes . for the fixed point is repelling , whereas for it is attracting . in the former case , the next fixed point of eq . ( [ rateeqgen ] ) is attractin

We study the extinction of an isolated single - species population after maintaining a long - lived state. We find that the rate equation is a convenient starting point for our analysis. In this case, the rate is derived as where is a smooth function determined by the specific gain - loss processes. The next fixed point of eqgen is attractin.

we investigate the phenomenon of extinction of a long - lived self - regulating stochastic population , caused by intrinsic ( demographic ) noise . extinction typically occurs via one of two scenarios depending on whether the absorbing state is a repelling ( scenario a ) or attracting ( scenario b ) point of the _ deterministic rate equation_. in scenario a the metastable stochastic population resides in the vicinity of an attracting fixed point next to the repelling point . in scenario b there


We have tested the reliability of the red giant branch ( rgb ) as a metallicity indicator...

the red giant branch ( rgb ) phase in intermediate- to low - mass stellar evolution corresponds to the phase just before the onset of helium fusion . during the rgb phase , a star contains an electron degenerate core surrounded by a hydrogen - burning shell fueled by the cno cycle . the color of the rgb on a color - magnitude diagram ( cmd ) strongly depends on the metal abundance of the stellar population ( e.g. ) . for this reason , the rgb has been widely used to obtain average metallicity estimates for a variety of stellar systems in the form of straightforward empirical calibrations between magnitude , color , and metallicity . however , the morphology and position of the rgb also depend somewhat on the age of the population , especially for stellar populations younger than gyr . thus , given an estimate for the age of a stellar population , the metallicity distribution function ( mdf ) of the system can be calculated by comparing the rgb with theoretical isochrones of the appropriate age or fiducial rgb sequences for discrete ages . previously , had investigated biases in determining the tip of the red giant branch ( trgb ) based in the galaxies lmc , smc , and lgs3 using synthetic cmds . that study investigated some population effects on metallicities derived from the synthetic cmds representing these systems . in this work , we provide a more thorough investigation of the degree to which star formation history can influence the results of these types mdf analyses mentioned above . to facilitate this , we generate model cmds with a variety of star formation histories ( sfhs ) and chemical evolution histories and calculate the mdfs by interpolating amongst a grid of isochrones . in section [ sec : meth ] , we outline the methods used , detailing how the synthetic cmds were created , how error and completeness profiles were applied , and how the interpolations were performed . results are presented in section [ sec : res ] , and we conclude our findings in sect

We present a new method for determining the tip of the red giant branch ( rgb ) in intermediate- to low - mass stellar evolution using synthetic cmds. We use a variety of star formation histories and chemical evolution histories to generate model cmd, which are interpolated amongst a grid of isochrones. The results are presented in section [ sec: meth ].

we have tested the reliability of the red giant branch ( rgb ) as a metallicity indicator accounting for observational errors as well as the complexity of star formation histories ( sfhs ) and chemical evolution histories observed in various stellar systems . we generate model color - magnitude diagrams ( cmds ) produced with a variety of evolutionary histories and compare the resultant metallicity estimates from the colors and magnitudes of rgb stars to the true input metallicities . we include


The xmm - newton survey science center is constructing a large ( 1000 sources ) and complete sample...

x - ray selection provides a well - proven and efficient mean of finding some of the astrophysically most interesting and energetic objects in the universe , like active galactic nuclei ( agn ) and clusters of galaxies . the xmm - newton survey science center ( ssc ) is assembling a large ( about 1000 sources ) sample of bright serendipitous xmm - newton sources at high galactic latitude ( ) , following well defined criteria ( completeness , representativeness , etc .. ) so as to allow both a detailed study of sources of high individual interest as well as statistical population studies . the sample , known as the xmm - newton bright serendipitous source sample " ( xmm - newton bss ) , is designed to have a flux limit of erg s in the 0.54.5 kev energy band . the major scientific goals of this project are to study the mix of different kinds of agn , and the cosmological evolution of clusters of galaxies . agn are expected to be the most numerous class of x - ray sources . the majority of the xmm - newton bss sources will have enough statistics ( hundreds of counts ) to allow x - ray spectral investigations ( see e.g. for the discovery of a type 2 agn from x - ray data only ) . such x - ray spectral information is fundamental to determine , source - by - source , the amount of metal absorption , the spectral shape , and the presence of reprocessed features ( e.g. fek line ) . moreover , at the x - ray limiting flux of the xmm - newton bss sample the optical counterparts of the x - ray sources have magnitudes bright enough to allow relatively high - quality optical and near - infrared spectroscopy even with a 4 meter class telescope . x - ray data , combined with optical and near - infrared spectroscopic information , will allow us to investigate the poorly understood relationships ( e.g. , ) between narrow- and broad - line agn in the optical regime , and absorbed and unabsorbed agn in the x - ray regime . the completeness of our sample should place our investigations

We present a large sample of bright serendipitous xmm - newton sources at high galactic latitude ( ). The sample is designed to have a flux limit of erg s in the 0.54.5 kev energy band, and will allow both a detailed study of sources of high individual interest as well as statistical population studies. We use the x - ray data from the ssc to investigate the mix of different kinds of active galactic nuclei and clusters of galaxies.

the xmm - newton survey science center is constructing a large ( 1000 sources ) and complete sample of bright serendipitous xmm - newton sources at high galactic latitude , so as to allow both the discovery of sources of high individual interest as well as statistical population studies . the sample , known as the xmm - newton bright serendipitous source sample " ( xmm - newton bss ) , has a flux limit of erg s in the 0.54.5 kev energy band and will be fundamental in complementing other medium a


We consider a crowd of persons trying to exit some area trough a small exit

when applications of natural sciences to human beings are considered , the problem of unpredictability of human mind is an eternal motif . in psychology , neurophysiological arguments overlap with philosophical ones . in sociology , the empiricistic foundations of natural sciences have been undermined by interpretative sociology of weber and simmel ; determinism is dead is a catchphrase of today . against this background , the modeling of crowd dynamics - which is our aim here - could seem to be an extreme example of a mechanicistic reductionism . on the other hand , prediction is an ultimate aim of all sciences ; here the famous statement on scientific aim savoir pour prvoir et prvoir pour pouvoir by auguste comte remains valid and desirable . in fact , a crowd can be seen as a many - body system with local interactions ; in such systems , statistical laws should allow for some predictions . once a comparison with experimental data became possible , the critique from the hermeneutically oriented audience is less convincing . + modeling of the crowd dynamics is known for more than 50 years . the methods have been advanced much in 90 s by dirk helbing and cooperators ; reviews and lists of references can be found in . among the methods , the social force model seems to be most realistic . this is a set of differential equations of motion , where positions and velocities of pedestrians are time - dependent variables ; the approach is equivalent to the molecular dynamics , where human desires are encoded in the form of social forces . within this model , a number of problems have been addressed , as lane formation , strip formation , turbulent waves , herding and bottlenecks . in this paper we address more directly to the problem of the phase of a simulated crowd . namely , we ask for the conditions when an individual or a small group can change their position with respect to their neighbours in the crowd . if they are stuck , we refer to a clogged phase . this criteri

We investigate the phase of a simulated crowd. In this paper, we consider the condition when an individual or a small group can change their position with respect to their neighbours in the crowd, and we find that the phase is clogged.

we consider a crowd of persons trying to exit some area trough a small exit . the probability is calculated that an individual is able to withdraw from the crowd under one s own steam . the problem is simulated within the generalized force model ( d. helbing et al . , nature 407 ( 2000 ) 487 ) , and all model parameters are taken from this paper . the results indicate , that in a crowd of 150 persons , this probability is not greater than ten percent . we also evaluate the number of helpers nece


We present a new proof of the quantum cramer - rao bound for precision parameter estimation and...

high sensitivity parameter estimation is an active area of research in quantum physics . there is growing effort both theoretically and experimentally to use quantum properties of matter to improve the precision with which a given parameter may be estimated . these ideas have been used in several problems of practical interest ; namely , clock synchronization , reference frame alignment , phase estimation , frequency measurements , position measurements and magnetometry . the simplest procedure for parameter estimation uses a probe which is coupled to the external field ( ) to be measured by a hamiltonian . the probe is prepared in a well - known initial state and then interacts with the field for a time before the measurement of a suitable observable . the process is then repeated for a large number of times ( ) to improve statistics . many different strategies have been proposed to improve the sensitivity limit of the simple parameter estimation procedure . for example , the probe can be a composite system or be augmented by ancillary systems used for multiple quantum non - demolition ( qnd ) measurements . the external field hamiltonian can be manipulated by additional field - independent and controllable hamiltonians to obtain an effective hamiltonian . during the evolution time many positive operator valued measurements ( povms ) can be performed and the results of the measurements used in a feedback loop . the only constraint on the metrology procedure is that a single measurement time is limited to . this assumption is physically motivated as any measurement process suffers from decoherence that limits the sensing time . the quantum cramer - rao bound gives a bound on the achievable sensitivity . for any measurement scheme , if the largest and smallest eigenvalues of are and , respectively , the optimum possible sensitivity is bounded by : where is the number of measurement runs and we set . this is very similar to the heisenberg limit for precision measureme

We present a new method for parameter estimation of the external field by using a probe coupled to the external Field. This technique is based on the heisenberg limit for precision measureme. The method is characterized by a hamiltonian which is controlled by additional field - independent and controllable hamiltonians. We show that the hamILtonian can be used to obtain an effective hamilltonian, which is a very similar to the Heisenberg Limit for precision measurement.

we present a new proof of the quantum cramer - rao bound for precision parameter estimation and extend it to a more general class of measurement procedures . we analyze a generalized framework for parameter estimation that covers most experimentally accessible situations , where multiple rounds of measurements , auxiliary systems or external control of the evolution are available . the proof presented demonstrates the equivalence of these more general metrology procedures to the simplest optimal


Epidemic dynamics in a stochastic network of interacting epidemic centers is considered

epidemic outbreak in a populated center or in a network of populated centra develops stochastically due to random interaction between individuals inside a center and due to a random migration between centers of the network . conventionally , an epidemic outbreak in a highly populated center is described by deterministic processes in according with law of large numbers ( lln ) . the mean field approximation ( hydrodynamic limits ) of the appropriate statistical models establishes the basic relation of stochastic description to the dynamical equations , say the sir model ( susceptible / infected/ removed ) and its more sophisticated modifications ( seir , sis , msir , etc . ) however , there are two important cases when stochastic effects are essential . firstly , it is obviously important when the populations in centers are not large . the second less obvious scenario can occur at the initial stage of outbreak when the number of infectives is small , then the discreteness of population can essentially affect the dynamics of the outbreak making it stochastic . for an isolated center , this case is thoroughly studied in . analysis of a network of interacting epidemic centers requires an account of migration fluxes between them . so , if the initial number of infectives triggering the outbreak in a particular populated center is small ( that is typical for many outbreaks ) than the lln fails at least at initial stage until the number of infectives is large enough . for this reason the observed number of infectives can be significantly different from the prediction of a deterministic model , i.e. the standard deviation of the number of infectives and the peak outbreak time can be wide even in highly populated center or a network of such centers . in principle , the probability density function ( pdf ) , its standard deviation , and other important characteristics for the outbreak forecast could be determined by a direct numerical simulation . however , this simulation ma

We study the stochastic dynamics of an epidemic outbreak in a highly populated center or in a network of populated centers. The probability density function ( pdf ) is calculated by a direct numerical simulation, which can be used to predict the peak outbreak time and the standard deviation of the number of infectives. We find that the maximum likelihood of the initial number of infectious diseases is small, but the mean field approximation ( hydrodynamic limits ) of the appropriate statistical models is not large enough.

epidemic dynamics in a stochastic network of interacting epidemic centers is considered . the epidemic and migration processes are modelled by markov s chains . explicit formulas for probability distribution of the migration process are derived . dependence of outbreak parameters on initial parameters , population , coupling parameters is examined analytically and numerically . the mean field approximation for a general migration process is derived . an approximate method allowing computation of


Using the overlap - dirac operator proposed by neuberger , we have computed in lattice qcd the one...

in recent years remarkable progress has been made towards formulations of lattice fermions which have no doublers and possess an exact chiral symmetry without giving up desirable features like flavor symmetry , locality , unitarity or gauge - invariance . the ginsparg - wilson relation has been recognized as the fundamental condition in this context , and a dirac operator which satisfies this relation can indeed describe chiral fermions on the lattice . one of the possible solutions of the ginsparg - wilson relation has been found by neuberger starting from the overlap formalism . in the massless case the overlap - dirac operator is , \ ] ] where in terms of the usual wilson - dirac operator , \ ] ] .\ ] ] in the range the right spectrum of massless fermions is obtained . for a quark of bare mass the overlap - dirac operator becomes since additive mass renormalization is forbidden , one avoids altogether a source of systematic errors that is always present with wilson fermions . lscher has shown that a fermion obeying the ginsparg - wilson relation possesses an exact chiral symmetry of the general form a fully legitimate form of global chiral symmetry is thus preserved for finite lattice spacing . the expected value of the global anomaly ( which comes from the non - invariance of the fermionic integration measure under the transformations above ) , the atiyah - singer index theorem on the lattice and the chiral ward identities are then fully attained before taking the continuum limit . thus , the central point in this framework is not to insist on the lattice form of the canonical chiral transformations ( in fact actions satisfying eq . ( [ eq : gw ] ) are not chirally invariant in the canonical sense ) , but rather be satisfied with a modified form of the chiral symmetry . the nielsen - ninomyia theorem is then circumvented altogether , and it is possible to define chiral fermions without doublers or breaking of flavor symmetry or other unpleasant drawbacks . the c

We present a new approach to the formulation of lattice fermions which have no doublers and possess an exact chiral symmetry without giving up desirable features like flavor symmetry, locality, unitarity or gauge - invariance. The ginsparg - wilson relation is a fundamental condition for formulating lattics which have zero doubler and have an exact form of global chirals. In this framework, we show that a fermion obeying the GINSCHAR - lattique relation can indeed describe.

using the overlap - dirac operator proposed by neuberger , we have computed in lattice qcd the one - loop renormalization factors of ten operators which measure the lowest two moments of unpolarized and polarized non - singlet quark distributions . these factors are necessary to extract physical numbers from monte carlo simulations made with overlap fermions . an exact chiral symmetry is maintained in all our results , and the renormalization constants of corresponding unpolarized and polarized


We present _ herschel _ far - infrared and submillimeter maps of the debris disk associated with...

true solar system analogues , systems of multiple planets with evidence for warm and cold dust disk components , have few representatives outside our own . a recently recognized exception is the hr 8799 ( an a5v star at 39.9 pc ) system which hosts a directly imaged multi - planet system and shows evidence for warm and cold dust disk components . four planetary companions have been detected around hr 8799 at projected separations of 15 , 24 , 38 and 68 au . evidence for a circumstellar dust disk has been known for some time , and _ spitzer _ observations have revealed that the disk must contain multiple dust components . found evidence for three disk components : a warm central component , an outer `` cold component '' extending from 90 - 300 au , and an external halo of small grains extending to an outer radius of 1000 au . the relatively young age of this system ( the most recent estimate gives an age of 20 - 50 myr , * ? ? ? * ) makes it especially intriguing , since this is the currently favored epoch for the formation of terrestrial planets . cccc 1342223848/9 & 9/10 july 2011 & pacsphoto 70/160 & 9018 2 + 1342223850/1 & 10 july 2011 & pacsphoto 100/160 & 7890 2 + 1342234924 - 28 & 18 dec 2011 & spirephoto & 169 5 [ obslog ] ccccc 70 & 5.5 x 5.8 & 5.1 & 0.4 & 0.338 + 100 & 6.7 x 6.9 & 4.45 & 0.5 & 1.43 + 160 & 10.7 x 12.1 & 9.55 & 0.6 & 8.90 + 250 & 18.7 x 17.5 & 0.3 & 4.0 & 25.16 + 350 & 25.6 x 24.2 & 0.3 & 3.4 & 29.01 + 500 & 38.2 x 34.6 & 0.3 & 4.8 & 20.70 [ obsdetails ] we also have an ideal viewing angle toward this system , as the orbital plane of the planets and disk appear to lie very close to the plane of the sky , although the inclination of the star has been estimated to be in excess of 40 by . a face - on geometry makes it possible to observe azimuthal variations in the disk structure , as well as radial ones ( e.g. , eri , and vega , , though see and ) . the presence of so many giant planets in a system makes it inevitable that the debris disk has

We present a new study of the hr 8799 system which hosts a multi - planet system with evidence for warm and cold dust disk components. We find that the system is a single - star system at 39.9 pc, and has a relatively young age. The planetary companions are found to be in the range of,, +, =, * _ spitzer _ ( a5v ), which is, in the, analogue of h 87 99.

we present _ herschel _ far - infrared and submillimeter maps of the debris disk associated with the hr 8799 planetary system . we resolve the outer disk emission at 70 , 100 , 160 and 250 and detect the disk at 350 and 500 . a smooth model explains the observed disk emission well . we observe no obvious clumps or asymmetries associated with the trapping of planetesimals that is a potential consequence of planetary migration in the system . we estimate that the disk eccentricity must be . as in


Tilted - axis cranking calculations have been performed for multi - quasiparticle states in well...

the moments of inertia of deformed atomic nuclei at low spins are a factor of two or three smaller than the rigid - body value . the reduction is attributed to the strong pair correlations , because nuclei in the ground state are in a superfluid condensed state . angular momentum is generated by either rotating the deformed superfluid or by breaking cooper pairs from this condensed state . in order to reach high spins , an increasing number of cooper pairs are broken , which reduces and finally quenches the pair condensate . it has been often stated that after this transition , the moments of inertia should reach the rigid - body value . however , this conjecture is based on the consideration of two special cases : ( i ) the limit of large particle number , where the nuclear shell structure becomes unimportant ; and ( ii ) nucleons in a harmonic oscillator potential at its equilibrium deformation . particularly for independent particles in a harmonic oscillator potential well , the moment of inertia has in the limit of vanishing angular velocity exactly the rigid - body value in any combination of stationary single - particle states provided the total energy is stationary with respect to volume - conserving variations of the equipotential ellipsoids . at finite angular velocity , the condition for the rigid - body value is that the second moments of the density distribution should have the ratio of the squares of the axes of the oscillator - plus - centrifugal equipotential ellipsoids , which is not exactly equivalent to a stationary energy . these results have led to the expectation that in real nuclei , the moment of inertia would not be very different from the rigid - body value if the pairing is quenched . this expectation was substantiated by early studies like , for example , that in ref. of more realistic single - nucleon potentials , which seemed to indicate that permitting the nuclear system to relax to an equilibrium shape generally tends to reduce deviati

We study the moments of inertia of deformed atomic nuclei at low spins. The moment of inersti is a factor of two or three smaller than the rigid - body value, and it is attributed to the strong pair correlations, because nucleions are in a superfluid condensed state. This result is based on the consideration of two special cases: ( i ) the limit of large particle number, where the nuclear shell structure becomes unimportant; and ( n ) nucleons.

tilted - axis cranking calculations have been performed for multi - quasiparticle states in well deformed a nuclei . in the limit of zero pairing , not only are the calculated moments of inertia substantially smaller than for rigid rotation , but also they are close to the experimental values . the moments of inertia are found to be insensitive to dynamic pair correlations .


We present a new dynamical model describing 3d motion in non axially symmetric galaxies

to study the dynamical behavior of galaxies it is necessary to build a model describing the properties of the system . information on the construction of dynamical models of galaxies are provided usually from observations , made after some necessary simplifying assumptions . on the other hand , it is a fact that galactic dynamical models are successful and realistic , only if the modeled characteristics agree with the corresponding observational data . in most cases , the galactic models are spherical or axially symmetric , in an attempt to simplify the study of orbits . for instance , in a spherical system all three components of the angular momentum and of course the total angular momentum is conserved . thus , we have a plane motion , which takes place in the plane perpendicular to the vector of the total angular momentum . on the other hand , in an axially symmetric system , where the motion is described by a potential the component of the angular momentum is conserved and the motion takes place in the meridional plane , which rotates non - uniformly around the axis of symmetry with angular velocity . spherical models for galaxies were studied by [ ,, ] . moreover , interesting axially symmetric galaxy models were presented and studied by [ ] . recently , [ ] used data derived from rotation curves of real galaxies , in order to construct a new axially symmetric model describing the motion in both elliptical and disk galaxy systems . of particular interest , are the so - called composite galactic dynamical models . in those models the potential has several components each describing a part of the system . such a dynamical model composed of four components , that is a disk , a nucleus , a bulge and a dark halo was studied by [ ] . a new composite mass model describing motion in axially symmetric galaxies with dark matter was recently presented and studied by [ ] . composite axially symmetric galaxy models describing the orbital motion in the galaxy were also studi

We study the dynamical behavior of galaxies in a composite galactic model. The potential has several components each describing a part of the system. We also study the motion in axially symmetric galaxis with dark matter.

we present a new dynamical model describing 3d motion in non axially symmetric galaxies . the model covers a wide range of galaxies from a disk system to an elliptical galaxy by suitably choosing the dynamical parameters . we study the regular and chaotic character of orbits in the model and try to connect the degree of chaos with the parameter describing the deviation of the system from axial symmetry . in order to obtain this , we use the smaller alingment index ( sali ) technique by numerical


We use detailed balance for a hadron composed of quark and gluon fock states to obtain parton...

there has been considerable interest in the flavor dependence of the proton s quark and antiquark distributions . the first measurement of the asymmetry was made by the nmc group . the integral of this distribution showed a violation of the gottfried sum rule . later , drell - yan and deep inelastic scattering experiments determined the bjorken- dependence of the asymmetry . the meson cloud model and the sullivan process were used to explain the momentum fraction distribution of ; many other models have been proposed . most recently , zhang and collaborators have used a simple statistical model to calculate the distribution in the proton . they consider the proton to be an ensemble of quark - gluon fock states , and use detailed balance or the principle of balance " to determine the distribution functions for all partons of the proton . despite its simplicity , the model does reasonably well in predicting the distributions of partons , as well as for that of . the excess of over comes about from the 2:1 ratio of u : d , which provides an excess of quarks for the annihilation of s . zhang , zou , and yang ( zzy ) write a general fock state expansion for the proton as with the number of pairs , the number of pairs and the number of gluons . the states are normalized such that the sum of the probabilities of finding a proton in the state summed over all , , and is unity , in zzy s statistical model , detailed balance between any two fock states requires that in which is the transfer rate of state into state . transfer rates between states are assumed to be proportional to the number of partons that can split or recombine . taking into account two processes , and , zzy find that this equation , together with the normalization condition ( [ norm ] ) , determines all the . it is clear from this equation that states , labelled by , are suppressed relative to states , labelled by . summing over all states , zhang et al . find , remarkably close to the experimental value of

We present a simple statistical model for the distribution of the proton in the presence of a large number of quark - gluon fock states. The model is based on the principle of balance, and it is able to predict the distributions of partons, as well as that of.

we use detailed balance for a hadron composed of quark and gluon fock states to obtain parton distributions in the proton and pion on the basis of a simple statistical model . + * parton distributions in the proton and pion * * mary alberg and ernest m. henley * + + _ department of physics , seattle university , seattle , wa 98122 , usa _ + _ institute for nuclear theory , university of washington , seattle , wa 98195 , usa _


This review is focussed on the outer halos of elliptical galaxies

in current hierarchical theories , elliptical galaxies represent an advanced stage of the galaxy formation process : they are massive galaxies found in dense environments . they reflect ` early ' conditions in galaxy formation as well as subsequent merging processes , making the study of their properties particularly interesting . however , their old stellar populations and complicated orbital structure make many important questions harder to answer for ellipticals than for spirals . this includes cosmological questions about their ages and precise formation mechanism , about the concentration of their dark matter halos , and the segregation of baryonic matter , as well as dynamical questions about the orbit distribution and total angular momentum , to name only a few . the subject of this review is the halos of elliptical galaxies and how planetary nebulae observations and dynamical modelling can help answer some of these questions . several other papers in this session elaborate on the topics discussed here . planetary nebulae ( pne ) are excellent test particles to trace the kinematics in the outer halos of elliptical galaxies . they occur as a brief stage in the late evolution of stars with masses between , when these stars evolve from the asymptotic giant phase to their final white dwarf stage . their nebular gas envelope converts up to 15% of the central star s radiation energy to photons in the characteristic [ oiii ] emission line [ 1 ] . from this emission line , pne can be identified and their radial velocities measured spectroscopically at distances of up to 2030 mpc . with 8 m class telescopes [ 2 ] or the special - purpose planetary nebula spectrograph ( pn.s ) [ 3 ] , several hundred pne have been found in giant elliptical galaxies with distance up to the virgo cluster . the pn number density approximately follows the surface density of stars ; thus a few tens of pne can be used to measure the stellar kinematics at several effective radii , where the s

We present a review of the halos of elliptical galaxies and how planetary nebulae observations can help answer some of these questions. In particular, we discuss the implications of planetary observations for galaxy formation and dynamics.

this review is focussed on the outer halos of elliptical galaxies . its emphasis is on ( i ) planetary nebulae as test particles to trace the stellar kinematics at large radii , ( ii ) the observed angular momentum in elliptical galaxy halos and its theoretical relevance , ( iii ) dynamical modelling of stellar - kinematic data , and ( iv ) a discussion of the evidence for dark matter halos in ellipticals from a wide range of measurements .


The interplay between local , repulsive interactions and disorder acting only on one spin...

experiments with optically controlled cold atoms are able to turn new concepts and theoretical models into reality. for example , the bose - hubbard hamiltonian was realized and the superfluid - insulator transition was observed, a fermionic mott insulator was created, anderson localization was detected, the spin hall effect was measured, and exotic features such as fractional statistics were perceived. in particular , such experiments make it possible to simulate models and discover phenomena which are absent in solid state physics . one such model , namely fermions on a lattice with spin - dependent hopping , was already realized. in another experiment a spin - dependent periodic potential was formed. a possible next step is to implement a lattice system with spin - dependent disorder by combining spin - dependent and local random potentials. spin - dependent disorder may , in principle , be realized experimentally by focusing light beams with different polarization on an optical lattice , after having been scattered from a diffusive plate. this leads to a spin - dependent , speckle - type effective random potential which is characterized by a short correlation length and pronounced statistical independence and which acts differently on particles with different spin orientation in the ground state . thereby spin - dependent speckle - type disorder modifies the local one - particle energies , hopping amplitudes , and interparticle interaction potentials . in this paper we discuss the anderson and mott metal - insulator transitions ( mit ) within the fermionic hubbard model in the presence of spin - dependent disorder . surprisingly , up to now the influence of such a type of disorder on correlated lattice fermions has not yet been investigated in detail . scalettar and collaborators analyzed the pairing instability in the attractive case , while the present authors studied the thermodynamical properties in the repulsive case. by employing the dynamical mean - field

We study the anderson and mott metal - insulator transitions ( mit ) in the fermionic hubbard model with spin - dependent disorder. We find that the andson and mot - metal insulators transitions are significantly affected by spin, while the mott metallic insulation transitions have a significant effect on the local one - particle energies, hopping amplitudes.

the interplay between local , repulsive interactions and disorder acting only on one spin orientation of lattice fermions ( spin - dependent disorder " ) is investigated . the nonmagnetic disorder vs. interaction phase diagram is computed using dynamical mean - field theory in combination with the geometric average over disorder . the latter determines the typical local density of states and is therefore sensitive to anderson localization . the effect of spin - dependent disorder is found to be


Student - generated multiple - choice questions ( mcqs ) revised by the instructor were used to...

both for students and researchers it is important to provide answers to already existing questions ; however , being able to properly formulate and to prioritize questions based on previous knowledge is of no lesser importance . the relevance of question posing in science is emphasized by a famous quote attributed to einstein : `` if i had an hour to solve a problem and my life depended on the solution , i would spend the first 55 minutes determining the proper question to ask '' . by way of contrast , traditional teaching has largely failed to promote the students question posing abilities . while traditional learning strategies based on instructor - generated questions , brain storming and drill - and - practice undoubtedly continue to be a must in the classroom , contemporary educational systems are increasingly placing emphasis on strategies assigning the student a more active role in learning and assessment processes . activities involving question - posing and answering are clearly one such strategy , the benefits of which have been widely documented in the existing literature on the subject . some of the above benefits are nicely summarized in ref . as follows : `` developing a deeper understanding of the subject content learned , shifting from acquiring to using knowledge , achieving a sense of ownership of the subject contents as well as their learning experience , developing higher order thinking skills , generating more diverse and flexible thinking , becoming more involved in ( and in control of ) their learning , facilitating small group communication regarding the interacting topic , building up self - confidence about the subject matter and developing interest and ability in the follow - up problem - solving activity ( ... ) . in addition , problem - posing has value for the instructors of the classes as well , particularly because it reveals insight into students abilities with the subject content and helps to provide an accurate assessment of what l

We present a study of the effects of question - posing on students in the context of science and mathematics. We show that the use of question- posed questions is an effective way to improve students ' knowledge of the subject, which is important for their learning and assessment processes.

student - generated multiple - choice questions ( mcqs ) revised by the instructor were used to design an educational game and to set part of the exam in the framework of an elementary course in photonics . an anonymous survey among the students revealed their general satisfaction with the method . the exam results of students who had been asked to author mcqs were compared to those of a control group subject to traditional teaching . the results of the former in the mcq test of the exam were si


We present an alternative technique for measuring the precursor masses of transient events in stars...

energetic and luminous transients mark the final stages of massive stars evolution . these transients include core - collapse explosions leading to type ii and ib / c supernovae ( sne ) , luminous blue variable ( lbv ) outbursts , and other more mysterious transients such as the optical transients in ngc 300 and ngc 6946 ( sn 2008s ; * ? ? ? * ) . current stellar evolution models indicate that the mapping between progenitor stars and the type of supernova is determined primarily by the zero age main - sequence mass and the star s mass - loss history . the theoretical expectations are that the most massive stars ( ) experience tremendous mass loss at the end of their lives , expelling their hydrogen and/or helium envelopes before exploding as sn type ib / c ; somewhat less massive stars ( ) are assumed to lose less mass as they evolve , and explode as sn type ii with their hydrogen envelopes intact . this picture is supported by observations . on the other hand , theoretical expectations for the progenitors of optical transients such as ngc 300 ot2008 - 1 and sn 2008s are lacking . empirically , lbvs are expected to be and estimates for ngc 300 ot2008 - 1 and sn 2008s place the progenitor mass somewhere between 6 and 20 . however , it is unclear whether the latter are sne resulting from the collapse of o / ne cores ( hereafter referred to as electron - capture sne ; * ? ? ? * ; * ? ? ? * ; * ? ? ? * ) , an extension of the lbv outburst phenomena to lower masses , or a new class of transient due to an unknown mechanism . at this juncture , progress in understanding the origins of these transients would be aided by the addition of observational constraints . the increasing prevalence of time - domain observations is adding to the number of transients identified , but the most basic property of the transients their stellar mass remains largely unknown . one approach to constraining the masses of the stars showing transients is to use precursor imaging ( e.g. , * ? ? ? i

We present a new study of the origins of luminous blue variable ( lbv ) transients in ngc 300 and ngca 6946. We find that the lv outbursts are a result of the collapse of o / ne cores, and that the progenitor stars have a mass loss history of around 6 to 20. This is consistent with the theory that the most massive stars experience mass loss at the end of their lives, expelling their hydrogen envelopes before exploding as.

we present an alternative technique for measuring the precursor masses of transient events in stars undergoing late stage stellar evolution . we use the well - established techniques of stellar population modeling to age - date the stars surrounding the site of the recent transient event in ngc 300 ( ngc 300 ot2008 - 1 ) . the surrounding stars must share a common turnoff mass with the transient , since almost all stars form in stellar clusters that remain physically associated for periods longe


In this note , we construct a non - constant continuous function r$ ] which cuts the real axis...

the relation between the measure theoretic and topological properties of canter set and generalized cantor sets are always surprising in their own right . in addition , the real valued functions on these sets have many applications in counterexamples . for example see for interesting applications of cantor sets and the related notions . the purpose of this note is to construct a continuous function   r$ ] which cuts the real axis uncountable times and it is not absolutely continuous . note that we say a continuous function   r$ ] cuts the real axis at if and for each open interval of , there exist some points and such that and . recall that a function   r$ ] is said to be _ * absolutely continuous * _ if for each there exists such that whenever are pairwise disjoint open subintervals of $ ] for which . we construct a sequence of continuous functions on $ ] such that whose uniform limit is the desired function . first , divide the interval $ ] to three equal segments . define on $ ] as follows : it is easy to see that is continuous and it s graph is an isosceles triangle with the height . draw this triangle on the intervals $ ] and $ ] every other one , symmetrically . let be the function on $ ] whose graph is as above . from now on , our aim from upper(lower ) triangle in each step is those triangles that their corresponding function s values are positive(negative ) , respectively . for construction of , fix the lower triangle drawn on the interval $ ] in the graph of and divide both intervals $ ] and $ ] to three equal segments . now , define the function on the interval $ ] as follows : it is not difficult to verify that is continuous and it s graph is an isosceles triangle with the height . now , draw this triangle on the intervals $ ] and $ ] every other one , symmetrically . then , copy the obtained graph on the interval $ ] , on the interval $ ] exactly and suppose that the obtained graph on the interval $ ] is . for the step 3 , fix two lower triangles drawn

We construct a continuous function on $ ] which cuts the real axis uncountable times and it is not absolutely continuous. For each open interval of, there exist some points and such that and. We construct an sequence of continuous functions on $] such that whose uniform limit is the desired function. First, divide the interval $ ]. We construct the function on$ ] as follows: it is easy to see that is continuous and it s graph is an isosceles triangle with the height. Now, draw this triangle on the intervals $.

in this note , we construct a non - constant continuous function   r$ ] which cuts the real axis uncountable times and also it is not absolutely continuous . functions of this type are very scarce in the literature .


A phenomenological kinetic energy theory of buoyant multiphase plumes is constructed , being...

the motivation for studying bubble plumes is evident , from the fact that these plumes are encountered in a variety of engineering problems . to mention a few , plumes have been used to damp sea waves in harbours ( pneumatic breakwaters ) , to prevent surface ice formation in harbours , to mix stratified fluid layers , to re - aerate lakes , and finally to protect installations from shock waves produced by underwater explosions ( cf . , for instance , bhaumik , 2005 ) . with increasing subsea activities plumes have acquired increased importance from a risk assessment point of view . it becomes imperative to obtain knowledge about the implications of a rupture , or even a breakage , of a subsea pipeline . thus in case of an underwater blowout of inflammable gas , one wishes answers to the following questions : what is the concentration of gas at the free surface ? what is the extension of the area covered by gas at the free surface ? what is the rising time of the gas ? the aim of the present work is to provide a theoretical framework from which answers to these questions can be given , in a quick and reasonably accurate way . our approach is based on the kinetic energy method , proposed by one of the present authors some years ago in the case of air - bubble plumes ( brevik 1977 , 1996,1999 ) . the essential generalization of the present paper is that we allow for dissolution of the gas . therewith a realistic answer to the first question above becomes in principle obtainable . especially when the plume is arising from large depths , the gas dissolution is expected to be an important factor . figure 1 sketches a plume coming from a gas release at depth . it is useful to divide the plume into three different zones : the zone of flow establishment ( zfe ) is characterized by high gas concentration and flow conditions changing rapidly with the height above the real source ( we thus do not introduce a virtual source being displaced some distance downward from the real s

We present a theoretical framework for the theory of bubble plumes. It is based on the kinetic energy method proposed by one of the present authors some years ago in the case of air - bubble plume ( brevik 1977, 1996,1992 ). The aim of this paper is to provide a realistic answer to the first question above, in a quick and reasonably accurate way.

a phenomenological kinetic energy theory of buoyant multiphase plumes is constructed , being general enough to incorporate the dissolution of the dispersive phase . we consider an axisymmetric plume , and model the dissolution by means of the ranz - marshall equation in which there occurs a mass transfer coefficient dependent on the plume properties . our kinetic energy approach is moreover generalized so as to take into account variable slip velocities . the theoretical model is compared with v