Non-equilibrium thermodynamics of marginal- and conditional-open chemical systems

Every open chemical system treated in this paper is restricted to the case involving a sequence of monomolecular reactions. Various kinds of probability distribution governing it are introduced according to the situations in which it is placed. The chemical system subject to marginal distribution is given the term marginal-open system MO. The open chemical system ō discussed by Nicolis and Babloyantz can be regarded as the limiting system of MO. For an open chemical system, itself in contact with an external reservoir of finite volume, the probability distribution conditioned on the marginal distribution for the external reservoir in an arbitrarily fixed state is more appropriate. Such an open chemical system is called a conditional-open system CO. However, in the case of the external reservoir of infinite volume, although it is not certainly trivial, another conditional probability distribution has to be proposed; it is derived on the hypothesis that the probability distribution for an arbitrary total number of molecules in the open chemical system is known. The open chemical system so specified is called conditional-open system $\text{C}\text{O}\text{?}$. It is shown that for each system $\text{MO, CO}\text{and}\text{C}\text{O}\text{?}$ the change of entropy starting from the steady state provides a Liapunov function under some conditions and that the steady state is asymptotically stable. The relation of the entropy change to non-equilibrium fluctuations of chemical components in each system is discussed in comparison with that in the corresponding open chemical system ō, for which the steady state surely exists and is always stable. It is shown that the concept of $\text{C}\text{O}\text{?}$ is useful for investigating the phenomenon of steady-state coupling.     

Prediction of surface area in polydisperse gas-suspension systems with variable apparent surface tension,viscosity and density

Bubble size distribution was found to be represented by a modified log-normal distribution with 3 parameters. The parameters are simple functions of suspension properties,viz. surface tension, viscosity and density, and a function of superficial gas rate. Correlations are presented, enabling the prediction of the distribution constants (and thus of the bubble size distribution) from the system properties and gas rate. Model translucent systems can be used, having identical apparent system properties as real suspensions in experimental work. A computer algorithm is presented for (i) prediction of bubble size distribution, defining the region of formation of spherical bubbles, (ii) converting particle size distribution into volume distribution, (iii) determining the actual gas volume from a hold-up correlation, and (iv) giving the surface area of the system of a given predicted distribution.     

Accumulation and Fate of Microorganisms and Microspheres in Biofilms Formed in a Pilot-Scale Water Distribution System

The accumulation and fate of model microbial “pathogens” within a drinking-water distribution system was investigated in naturally grown biofilms formed in a novel pilot-scale water distribution system provided with chlorinated and UV-treated water. Biofilms were exposed to 1-μm hydrophilic and hydrophobic microspheres, Salmonella bacteriophages 28B, and Legionella pneumophila bacteria, and their fate was monitored over a 38-day period. The accumulation of model pathogens was generally independent of the biofilm cell density and was shown to be dependent on particle surface properties, where hydrophilic spheres accumulated to a larger extent than hydrophobic ones. A higher accumulation of culturable legionellae was measured in the chlorinated system compared to the UV-treated system with increasing residence time. The fate of spheres and fluorescence in situ hybridization-positive legionellae was similar and independent of the primary disinfectant applied and water residence time. The more rapid loss of culturable legionellae compared to the fluorescence in situ hybridization-positive legionellae was attributed to a loss in culturability rather than physical desorption. Loss of bacteriophage 28B plaque-forming ability together with erosion may have affected their fate within biofilms in the pilot-scale distribution system. The current study has demonstrated that desorption was one of the primary mechanisms affecting the loss of microspheres, legionellae, and bacteriophage from biofilms within a pilot-scale distribution system as well as disinfection and biological grazing. In general, two primary disinfection regimens (chlorination and UV treatment) were not shown to have a measurable impact on the accumulation and fate of model microbial pathogens within a water distribution system.     

The stochastic community and the logistic-J distribution

A new formal model called the multispecies logistical (MSL) system produces species/abundance distributions that are compared statistically with those found in natural communities. The system, which is able to handle thousands of individuals from hundreds of species, iteratively selects random pairs of individuals and transfers a unit of biomass (or energy) between the respective species. Several elaborations of the model, including those with trophic compartments, appear to produce the same distribution. The theoretical distribution underlying the MSL system is a hyperbolic section, here called the logistic-J distribution. In the study reported here, the logistic-J distribution has been fitted to the species-abundance histograms of 125 randomly selected taxocoenoses. Since the overall chi square score of the logistic-J achieved near-optimality in this study, it cannot be distinguished statistically from the J-curves observed by field biologists. For comparison, the log-series distribution was given the same test and scored significantly higher (more poorly) than the mean logistic-J score. If there is a single, major distribution underlying natural communities, it is not the log-series distribution. Nor, owing to a mathematical error in its formulation, can it be the lognormal distribution. In the MSL system each species follows a “stochastic orbit” about the mean abundance producing, in consequence, the logistic-J distribution. Such orbits are produced by any system in which the probabilities of reproduction and death are approximately equal. Accordingly, the “stochastic communities hypothesis” is proposed here as the overall mechanism governing abundances in all natural communities. It is not a single mechanism, per se, but the net effect of all environmental influences.     

Origins of Pareto distribution in nonlinear dynamic systems

The Pareto distribution, whereby at large enough x the probability density ρ(x) ～ x ? α (α ≥ 2), is quite important in both basic and practical aspects. The main point is its essential difference from the normal (Gaussian) distribution; namely, the probability of large deviations in this case proves to be much higher. Universal applicability of the normal distribution law remains a common belief despite the lack of objective proof in many applied areas. Here we consider how a Pareto distribution arises in a dynamic system exposed in a noise field, and discuss simplest unidimensional models where the system response in a broad range of the variable can be accurately enough approximated with such a distribution.     

青菜-土壤生态系统中氚水的迁移与分布动态

采用模拟污染物的同位素示踪技术研究了两种引入方式（模拟灌溉和降雨）下氘水在青菜-土壤模拟生态系统中的迁移与分布动态,测定了植物和土壤样品中两种形态氚（自由水氚和结合态氚）的比活度,以探明氚水在青菜-土壤系统中的行为特性,不同引入方式对青菜吸收和积累氚水的影响,结果显示：引入土壤中的氚水,不仅在系统各分室间转移和分配,而且迅速向系统外散逸,以自由水氚和结合态氚形式存在于青菜组织中,以吸湿性水氚和结晶水氚存在于土壤,其中自由水氚（或吸湿性水氚）远大于结合态氚（或结晶水氚）;青菜茎中的总氚比活度高于叶和根中的比活度,运用示踪动力学分室模型原理对实验数据进行拟合得;土壤中的比活度C5（模拟灌溉）=91.59e^-0.1002t 99.91e^-9.1105t和Cs(模拟降雨）=78.09e^-0.5115t 48.27e^-0.0475t;青菜植株中的比活度Cv(模拟灌溉）=543.52(e^-0.1002t-e^-9.1105t)和Cv(模拟降雨）=647.07e^-0.5115t 241.28e^-0.0475t;方差分析结果表明各回归方程较好地反应了氚水在青菜-土壤系统中的变化动态。     

Using PG-Liposome-Based System to Enhance Puerarin Liver-Targeted Therapy for Alcohol-Induced Liver Disease

A critical issue for alcohol-induced liver disease (ALD) therapeutics is the lack of a highly efficient delivery system. In this study, a Puerarin-propylene glycol-liposome system was prepared for the purpose of targeting puerarin, an isoflavon, to the liver. Transmission electron microscope (TEM) results showed the liposomes to be spherical in shape with an average diameter of 182 nm with a polydispersity index of 0.239. The zeta potential of the particles was about ?30 mV. The entrapment efficiency of puerarin was above 90%. MTT-based assay in HpeG2 cells showed no significant cytotoxicity in the presence of up to 25% concentration of the system containing 3% puerarin. In vivo performance of this system was studied in mice. Pharmacokinetics and distribution of puerarin-PG-liposome system was studied relative to puerarin solution at the same dose levels. The results show that puerarin-PG-liposome prolonged drug retention time and decreased elimination of puerarin in mice (AUC of liposome system and solution was 9.5 and 4.0 mg h L^?1, respectively). Furthermore, propylene glycol (PG)-liposome system enhanced puerarin distribution into liver and spleen, while decreasing puerarin distribution in other tissues. Overall, the puerarin-PG-liposome system showed enhanced therapeutic effect in mice with ALD.     

Resource distribution and its effect on the mating system of a longhorned beetle,Perarthrus linsleyi (Coleoptera: Cerambycidae)

Summary Adults of Perarthrus linsleyi feed on flowers of creosote bush, Larrea tridentata. Mating also occurs on the flowers and foliage of this plant. This food resource is widely and evenly distributed in space, and is usually abundant. The spatial distribution of the beetles bore no relationship to the spatial distribution of flowers among creosote bushes, nor were female beetles distributed predictably with respect to flower distribution. Males moved widely over the area under study, and moved much more frequently than females. Males actively searched for females, and mounted and began copulation attempts without preliminary courtship. Males did not engage in aggressive defense of females, creosote flowers, or creosote bushes. This species exhibits a scramble competition mating system. The spatial distribution of the food resource is a primary factor in the evolution of the mating system of Perarthrus linsleyi.     

Electron microscopy of beaded agarose gels

Electron microscopy has been carried out on sections of beaded agarose with a wide range of thicknesses, and the results have been analyzed by means of stereological theory using computer graphics. The results agree with a randomly orientated system in which, for 4% gels, the mean molecular weight per unit length of the fiber system is 110 kg mol^?1 nm^?1, and the number average interjunction length is 37 nm, with an asymmetrical distribution resembling a Maxwell-Boltzmann distribution. The spatial distribution of the structure is not uniformly random and there seem to be mi microvoids.     

Monoamines and reproduction in Pecten maximus,a preliminary approach

Summary

The distribution of serotonin-like immunoreactivity was studied in the central nervous system and the gonad of Pecten maximus. Cerebral and pedal ganglia contain a well developed serotonin-immunoreactive neuronal subpopulation, whereas positive neurons are scarce in the visceral ganglion. The distribution pattern of immunoreactive elements in the gonad indicate that serotonin is involved in peripheral neurotransmission of this organ. Seasonal variations of monoamines (serotonin, dopamine and noradrenaline) have been investigated in the nervous system using HPLC. Lower concentrations of serotonin are observed during winter in the central nervous system; dopamine levels of the visceral ganglion are correlated to gonadal growth.     

On the stochastic theory of compartments: Solution forn-compartment systems with irreversible,time-dependent transition probabilities

The bivariate distribution of a two-compartment stochastic system with irreversible, time-dependent transition probabilities is obtained for any point in time. The mean and variance of the number of particles in any compartment and the covariance between the number of particles in each of the two compartments are exhibited and compared to existing results. The two-compartment system is then generalized to ann-compartment catenary and to ann-compartment mammillary system. The multivariate distributions of these two systems are obtained under two sets of initial conditions: (1) the initial distribution is known; and (2) the number of particles in each compartment of the system at timet=0 is determined. The moments of these distributions are also produced and compared with existing results.     

Effect of freshwater discharge, intrusions of coastal water, and bathymetry on zooplankton distribution in a Norwegian fjord system

Freshwater discharge from a hydroelectric power plant had astrong impact on plankton transport and distribution withinthe fjord system. Most zooplankters submerged beneath the outgoingbrackish current, and subsequent advection by the compensationcurrent caused high concentrations near the power plant outlet.Currents driven by wind-induced changes in the density fieldin the adjacent coastal waters dominated transport between thefjord system and Outer regions. Normal plankton advection ratesappeared to be on the same order of magnitude as local zooplanktongrowth within the fairly enclosed system. However, during strong,short-term intrusions of coastal water, plankton compositionand distribution changed markedly in the course of a few days.The bathymetry seemed to be decisive for the distribution ofAcartia, which was recurrently found in highest numbers at theshallowest sampling location.     

Two-Level Incremental Checkpoint Recovery Scheme for Reducing System Total Overheads

Long-running applications are often subject to failures. Once failures occur, it will lead to unacceptable system overheads. The checkpoint technology is used to reduce the losses in the event of a failure. For the two-level checkpoint recovery scheme used in the long-running tasks, it is unavoidable for the system to periodically transfer huge memory context to a remote stable storage. Therefore, the overheads of setting checkpoints and the re-computing time become a critical issue which directly impacts the system total overheads. Motivated by these concerns, this paper presents a new model by introducing i-checkpoints into the existing two-level checkpoint recovery scheme to deal with the more probable failures with the smaller cost and the faster speed. The proposed scheme is independent of the specific failure distribution type and can be applied to different failure distribution types. We respectively make analyses between the two-level incremental and two-level checkpoint recovery schemes with the Weibull distribution and exponential distribution, both of which fit with the actual failure distribution best. The comparison results show that the total overheads of setting checkpoints, the total re-computing time and the system total overheads in the two-level incremental checkpoint recovery scheme are all significantly smaller than those in the two-level checkpoint recovery scheme. At last, limitations of our study are discussed, and at the same time, open questions and possible future work are given.     

Distribution of FMRFamide-like immunoreactivity in the nervous system of the slug Limax maximus

Summary The distribution of FMRFamide-like immunoreactive neurons in the nervous system of the slug Limax maximus was studied using immunohistochemical methods. Approximately one thousand FMRFamide-like immunoreactive cell bodies were found in the central nervous system. Ranging between 15 m and 200 m in diameter, they were found in all 11 ganglia of the central nervous system. FMRFamide-like immunoreactive cell bodies were also found at peripheral locations on buccal nerve roots. FMRFamide-like immunoreactive nerve fibres were present in peripheral nerve roots and were distributed extensively throughout the neuropil and cell body regions of the central ganglia. They were also present in the connective tissue of the perineurium, forming an extensive network of varicose fibres. The large number, extensive distribution and great range in size of FMRFamide-like immunoreactive cell bodies and the wide distribution of immunoreactive fibres suggest that FMRFamide-like peptides might serve several different functions in the nervous system of the slug.     

扬子鳄消化系统组织学和细胞学研究概况

综述了扬子鳄消化系统的组织结构、超微结构、内分泌细胞种类与密度分布等,得出3个方面的结论：①从消化系统组织和细胞的演化程度看,扬子鳄尚属较原始的类群;⑦扬子鳄消化系统组织结构、细胞的超微结构和内分泌细胞的种类与分布有较大的特异性;②扬子鳄消化系统组织和细胞的结构与功能间其取食习性是适应的。还对今后的研究工作提出了建议。     

A model for hydranth regeneration inTubularia

Pigment distribution presages hydranth regeneration in the marine hydroidTubularia. We suggest that such a distribution could result from a reaction-diffusion system. A model system based on a practical reaction scheme is studied and spatial structures found which closely resemble this pigment distribution. Finite-amplitude spatial structures in reaction-diffusion systems are considered. Whereas in one spatial dimension the final structures are normally very similar to the transient patterns which emerge from a linear analysis, it is shown that in more than one dimension this is not necessarily the case. The reasons for this are discussed.     

Quasi-stationary and ratio of expectations distributions: A comparative study

Many stochastic systems, including biological applications, use Markov chains in which there is a set of absorbing states. It is then needed to consider analogs of the stationary distribution of an irreducible chain. In this context, quasi-stationary distributions play a fundamental role to describe the long-term behavior of the system. The rationale for using quasi-stationary distribution is well established in the abundant existing literature. The aim of this study is to reformulate the ratio of means approach ( [Darroch and Seneta, 1965] and [Darroch and Seneta, 1967]) which provides a simple alternative. We have a two-fold objective. The first objective is viewing quasi-stationarity and ratio of expectations as two different approaches for understanding the dynamics of the system before absorption. At this point, we remark that the quasi-stationary distribution and a ratio of means distribution may give or not give similar information. In this way, we arrive to the second objective; namely, to investigate the possibility of using the ratio of expectations distribution as an approximation to the quasi-stationary distribution. This second objective is explored by comparing both distributions in some selected scenarios, which are mainly inspired in stochastic epidemic models. Previously, the rate of convergence to the quasi-stationary regime is taking into account in order to make meaningful the comparison.     

Age distribution of trees in stationary forest system

A statistical theory for the age distribution of spatially dominant trees in a stationary forest system is developed. The result depends whether or not mortality is spatially correlated, as well as whether or not the stand boundaries are pre-determined. In the case of spatially non-correlated mortality, the tree age distribution is an exponential with survival rate as the base. In the case of spatially correlated mortality within a stand with pre-determined boundaries, the age distribution within the stand is an exponential with natural base. For a small stand, the median life span of the stand is inversely proportional to the number of trees (n); the median life span in relation to stand closure time is inversely proportional to n ln(n). For a large stand, the stand life does not extend to the closure time.The behaviour of a forest system without fixed stand boundaries depends on the dimensionality of the system. In the case of a one-dimensional system, the longevity distribution is exponential, most of the trees however having the same longevity. Consequently, the probability density of tree age is constant. However, the probability mass of size of catastrophe destroying a particular tree is evenly distributed. This is due to trees being rapidly born on empty areas in the beginning of the life cycle, and clusters rapidly growing into larger ones close to the end of tree life.     

Influence of Metal of the Applicator on the Dose Distribution during Brachytherapy

This study explores how the metal materials of the applicator influence the dose distribution when performing brachytherapy for cervical cancer. A pinpoint ionization chamber, Monte Carlo code MCNPX, and treatment planning system are used to evaluate the dose distribution for a single Ir-192 source positioned in the tandem and ovoid. For dose distribution in water with the presence of the tandem, differences among measurement, MCNPX calculation and treatment planning system results are <5%. For dose distribution in water with the presence of the ovoid, the MCNPX result agrees with the measurement. But the doses calculated from treatment planning system are overestimated by up to a factor of 4. This is due to the shielding effect of the metal materials in the applicator not being considered in the treatment planning system. This result suggests that the treatment planning system should take into account corrections for the metal materials of the applicator in order to improve the accuracy of the radiation dose delivered.     

Product-Form Stationary Distributions for Deficiency Zero Chemical Reaction Networks

We consider stochastically modeled chemical reaction systems with mass-action kinetics and prove that a product-form stationary distribution exists for each closed, irreducible subset of the state space if an analogous deterministically modeled system with mass-action kinetics admits a complex balanced equilibrium. Feinberg’s deficiency zero theorem then implies that such a distribution exists so long as the corresponding chemical network is weakly reversible and has a deficiency of zero. The main parameter of the stationary distribution for the stochastically modeled system is a complex balanced equilibrium value for the corresponding deterministically modeled system. We also generalize our main result to some non-mass-action kinetics.