Steady-state nucleation rate and flux of composite nucleus at saddle point

The steady-state nucleation rate and flux of composite nucleus at the saddle point is studied by extending the theory of binary nucleation. The Fokker-Planck equation that describes the nucleation flux is derived using the Master equation for the growth of the composite nucleus, which consists of the core of the final stable phase surrounded by a wetting layer of the intermediate metastable phase nucleated from a metastable parent phase recently evaluated by the author [J. Chem. Phys. {\bf 134}, 164508 (2011)]. The Fokker-Planck equation is similar to that used in the theory of binary nucleation, but the non-diagonal elements exist in the reaction rate matrix. First, the general solution for the steady-state nucleation rate and the direction of nucleation flux is derived. Next, this information is then used to study the nucleation of composite nucleus at the saddle point. The dependence of steady-state nucleation rate as well as the direction of nucleation flux on the reaction rate in addition to the free-energy surface is studied using a model free-energy surface. The direction of nucleation current deviates from the steepest-descent direction of the free-energy surface. The results show the importance of two reaction rate constants: one from the metastable environment to the intermediate metastable phase and the other from the metastable intermediate phase to the stable new phase. On the other hand, the gradient of the potential $\Phi$ or the Kramers crossover function (the commitment or splitting probability) is relatively insensitive to reaction rates or free-energy surface.Comment: 12 pages, 6 figures, to be published in Journal of Chemical Physic

On Psychotic Phenomena and Unruliness: studies on the childhood risk for severe mental illness

Psychiatric disorders in adulthood, including severe mental illnesses, commonly have antecedents in childhood or adolescence. A better understanding of the developmental pathways of psychiatric problems in early childhood might help to achieve a more comprehensive understanding of severe mental illness in adults. The general aim of this thesis was to gain insights into the neurodevelopmental pathways of children at increased risk for severe mental illness. Here we focussed on two prevalent yet impairing psychiatric phenotypes of childhood: psychotic phenomena and disruptive behaviour problems. Each of these constellations of psychiatric symptoms is in its own right predictive of substantially poorer psychosocial functioning in the long term. All studies described in this thesis were conducted in the context of the Generation R Study, a population-based cohort study in Rotterdam, the Netherlands. The findings and interpretations of the individual studies are discussed in the broader context of the existing literature. More specifically, several methodological considerations are discussed pertaining to the neurodevelopmental model of psychosis, the neurodevelopmental model of disruptive behaviour, analytical methods of behavioural heterogeneity, assessment of psychotic experiences in children and the link between cannabis use and psychopathology. We conclude with several recommendations for improved clinical practice and future research

An integral equation approach to effective interactions between polymers in solution

We use the thread model for linear chains of interacting monomers, and the ``polymer reference interaction site model'' (PRISM) formalism to determine the monomer-monomer pair correlation function $h_{mm}(r)$ for dilute and semi-dilute polymer solutions, over a range of temperatures from very high (where the chains behave as self-avoiding walks) to below the $\theta$ temperature, where phase separation sets in. An inversion procedure, based on the HNC integral equation, is used to extract the effective pair potential between ``average'' monomers on different chains. An accurate relation between $h_{mm}(r)$, $h_{cc}(r)$ [the pair correlation function between the polymer centers of mass (c.m.)], and the intramolecular form factors is then used to determine $h_{cc}(r)$, and subsequently extract the effective c.m.-c.m. pair potential $v_{cc}(r)$ by a similar inversion procedure. $v_{cc}(r)$ depends on temperature and polymer concentration, and the predicted variations are in reasonable agreement with recent simulation data, except at very high temperatures, and below the $\theta$ temperature.Comment: 13 pages, 13 figures, revtex ; revised versio

Cytotoxicity of oleandrin isolated from the leaves of Nerium indicum Mill. on several human cancer cell lines

Finding anticancer drugs from natural resources still proceeds. Oleandrin isolated from Nerium indicum Mill. inhibited the growth of mieloma cell line in vitro better than that of vincristine sulphate. This study was aimed to determine the cytotoxic effect of oleandrin on various human cancer cell lines. Cytotoxic test of oleandrin on seven human cancer cell lines was done by SRB-method. The analysis was conducted by comparing the ID50 of oleandrin with that of doxorubicin and cisplatin as positive controls. This result indicated that oleandrin possessed the best cytotoxic effect on breast cancer (MCF7) with ID50 at 8.85 nM. Keywords : Oleandrin, cytotoxicity, human cancer cells, ID5

Hyper-Palatable Foods: Development of a Quantitative Definition and Application to the US Food System Database

Objective: Extensive research has focused on hyper-palatable foods (HPF); however, HPF are defined using descriptive terms (e.g., fast foods, sweets), which are not standardized and lack specificity. The study purpose was to develop a quantitative definition of HPF and apply the definition to the Food and Nutrient Database for Dietary Studies (FNDDS) to determine HPF prevalence in the US food system. Methods: A numeric definition of HPF was developed by extracting common HPF descriptive definitions from the literature and using nutrition software to quantify ingredients of fat, simple sugars, carbohydrates, and sodium. The definition was applied to the FNDDS. Results: HPF from the literature aligned with three clusters: (1) fat and sodium (> 25% kcal from fat, ≥ 0.30% sodium by weight), (2) fat and simple sugars (> 20% kcal from fat, > 20% kcal from sugar), and (3) carbohydrates and sodium (> 40% kcal from carbohydrates, ≥ 0.20% sodium by weight). In the FNDDS, 62% (4,795/7,757) of foods met HPF criteria. The HPF criteria identified a variety of foods, including some labeled reduced or low fat and vegetables cooked in creams, sauces, or fats. Conclusions: A data-derived HPF definition revealed that a substantial percentage of foods in the US food system may be hyper-palatable, including foods not previously conceptualized as hyper-palatable

A coil-globule transition of a semiflexible polymer driven by the addition of spherical particles

The phase behaviour of a single large semiflexible polymer immersed in a suspension of spherical particles is studied. All interactions are simple excluded volume interactions and the diameter of the spherical particles is an order of magnitude larger than the diameter of the polymer. The spherical particles induce a quite long ranged depletion attraction between the segments of the polymer and this induces a continuous coil-globule transition in the polymer. This behaviour gives an indication of the condensing effect of macromolecular crowding on DNA.Comment: 12 pages, 4 figure