Search results for "BIF"

Combined impacts of the Allee effect, delay and stochasticity: Persistence analysis

2020

Abstract We study a combined influence of the Allee effect, delay and stochasticity on the base of the phenomenological Hassell mathematical model of population dynamics. This bistable dynamical model possesses a wide variety of regimes, both regular and chaotic. In the persistence zone, these regimes coexist with the trivial equilibrium that corresponds to the extinction of the population. It is shown that borders of the persistence zone are defined by the crisis and saddle-node bifurcation points. Noise-induced transitions from the persistence to the extinction are studied both numerically and analytically. Using numerical modeling, we have found that the persistence zone can decrease and…

Dynamics of a minimal consumer network with bi -directional influence

2018

Abstract We study the dynamics of a model of interdependent consumer behavior defined by a family of two-dimensional noninvertible maps. This family belongs to a class of coupled logistic maps with different nonlinearity parameters and coupling terms that depend on one variable only. In our companion paper we considered the case of independent consumers as well as the case of uni-directionally connected consumers. The present paper aims at describing the dynamics in the case of a bi-directional connection. In particular, we investigate the bifurcation structure of the parameter plane associated with the strength of coupling between the consumers, focusing on the mechanisms of qualitative tr…

Bioavailability of zinc from infant foods byin vitro methods (solubility, dialyzability and uptake and transport by Caco-2 cells)

2006

The aim of this study was to evaluate the bioavailability of zinc from infant foods (adapted, follow-up and toddler milk-based formulas and fruit juices containing milk and cereals, FMC) using solubility, dialyzability and a model combining simulated gastrointestinal digestion and zinc uptake and transport by Caco-2 cells. The greater solubility of zinc from infant formulas compared with fruit juices (FMC) could be due to the greater casein phosphopeptide content resulting from casein hydrolysis. The highest zinc dialysis percentage corresponded to FMC, which on the other hand had the lowest zinc contents of the analyzed samples. The presence of organic acids in samples of this kind favors …

A whey-predominant formula induces fecal microbiota similar to that found in breast-fed infants

2007

To compare the effects of a whey-predominant infant formula and breast milk on the gut microbiota, growth, and tolerance of infants, we conducted an open, prospective, parallel-group study in healthy newborn infants. A total of 60 infants were enrolled, and 55 completed the study. Of the 55 infants, 21 were breast-fed and 34 were fed a whey-predominant study formula that had low phosphate concentration (31 mg/100 kcal), was reduced in protein (1.8 g/100 kcal or 0.43 g/kJ), had lactose as the sole carbohydrate source, and had an amino acid profile and buffering capacity similar to that of human milk. At 30 and 60 days of age, fecal bacterial counts were determined using fluorescence in situ …

COMPLICANZE DELL'OSTEONECROSI DEI MASCELLARI ASSOCIATE A TERAPIA CON BIFOSFONATI: ASPETTI TC ED RM

2008

Nutrient versus pollination limitation in Platanthera bifolia and Dactylorhiza incarnata (Orchidaceae)

2000

Availability of resources and pollination services have been demonstrated to have impact on reproductive success in some orchid species, but to our knowledge no studies have examined the effects of nutrient application and pollination limitation in the same experiment. In this study, factors limiting reproductive success were studied with two terrestrial orchid species in Central Finland during 1996 and 1997. In a field experiment using a factorial design, plants of nectar-producing Platanthera bifolia and nectarless Dactylorhiza incarnata were treated with nutrient application and hand-pollination. Inflorescence size was considered as an indicator of attractiveness to pollinators as well a…

Ship-in-a-bottle synthesis of triphenylamine inside faujasite supercages and generation of the triphenylamminium radical ion

2005

Abstract The ship-in-a-bottle synthesis of triphenylamine encapsulated within basic X zeolite has been accomplished by reacting sodium diphenylamide with bromobenzene in the presence of a bifunctional palladium (Hartwig–Buchwald conditions). The presence of incarcerated triphenylamine was demonstrated by dissolving the zeolite with concentrated HF and analyzing the organic material in the dichloromethane extract. Laser flash photolysis (266 nm) gives rise to the generation of triphenylamminium radical cation detected as a transient species decaying in hundreds of microseconds. Upon repetitive cyclic voltammograms, zeolite encapsulated triphenylamine shows a reversible oxidation–reduction pr…

Numerische Behandlung von Verzweigungsproblemen bei gew�hnlichen Differentialgleichungen

1979

We present a new method for the numerical solution of bifurcation problems for ordinary differential equations. It is based on a modification of the classical Ljapunov-Schmidt-theory. We transform the problem of determining the nontrivial branch bifurcating from the trivial solution into the problem of solving regular nonlinear boundary value problems, which can be treated numerically by standard methods (multiple shooting, difference methods).

Determination of 40 currently used pesticides in airborne particulate matter (PM 10) by microwave-assisted extraction and gas chromatography coupled …

2011

A confirmatory and sensitive procedure has been developed for the determination of 40 currently used pesticides (Cups) in airborne particulate matter (PM 10) at trace level. The proposed method includes extraction of PM 10-bound pesticides by microwave-assisted extraction (MAE) followed by a gel permeation chromatography (GPC) clean-up and determination by GC-MS/MS. The injection mode and the main parameters in MS/MS were optimized. The matrix effect was also evaluated. Recoveries ranged from 70 to 120% except for pyrimethanil and pirimicarb. The limit of quantification (LOQ) ranged from 1.32 to 39.47 pg m(-3), when air volumes of 760 m(3) were collected. The method was applied to 38 sample…

Metodes izstrāde polihlorēto bifenilu noteikšanai transformatoru eļļās izmantojot gāzu hromatogrāfiju

2016

Metodes izstrāde polihlorēto bifenilu noteikšanai transformatoru eļļās izmantojot gāzu hromatogrāfiju. Sprince L., zinātniskais vadītājs asoc. prof. Mekšs P. Maģistra darbs, 48 lappuses, 15 attēli, 15 tabulas, 32 literatūras avoti, 1 pielikums. Latviešu valodā. Darbā apkopota literatūrā pieejamā informācija par polihlorēto bifenilu īpašībām un to izmantošanu par piedevām transformatoru eļļās. Veikts šo savienojumu noteikšanas metožu izvērtējums un salīdzinājums. Izmantojot kapilāro gāzu hromatogrāfiju ar elektronu satveres detektoru, noteikts polihlorēto bifenilu saturs 32 transformatoru eļļas paraugos. Novērtēta eļļas matricas ietekme uz faktoriem, kas raksturo iegūto rezultātu pareizību, …