The prevalence of developmental defects of enamel (DDE) in the permanent dentition in developed countries has been reported to be in the range of 9–68 % and with no gender predilection. Several etiological factors have been implicated as being responsible for DDE in the permanent teeth. Although local, systemic, genetic or environmental factors have been attributed to DDE frequently they are li...

We consider a switching system with time delay composed of a finite number of linear delay differential equations (DDEs). Each DDE consists of a sum of a linear ODE part and a linear DDE part. We study two particular cases: (a) all the ODE parts are stable and (b) all the ODE parts are unstable and determine conditions for delay independent stability. For case (a), we extend a standard result o...

Developmental defects of enamel (DDE) are frequently observed. In both pediatric and orthodontic dental practices. DDE consist mainly of hypoplasia, diffuse and demarcated opacities.1 Often, a combination of enamel defects may be recognized in the same child (Fig. 1). Weerheijm et al. defined the term Molar Incisor Hypomineralization (MIH) to describe a more specific pattern of DDE: hypomineral...

Levels of organochlorine compounds in the blood plasma of after-second-year female peregrine falcons (Falco peregrinus) were determined from samples collected from southern Greenland in 1985 and western Greenland from 1983 to 1989, and from adult and nestling gyrfalcons (Falco rusticolus) from western Greenland in 1989 and 1990. Samples were taken during nesting. Levels of p,p'-DDE (DDE) in per...

The doctrine of double effect (DDE) is a moral principle that distinguishes between harm we cause as a means to an end and harm that we cause as a side-effect. As a purely descriptive matter, the DDE is well established that it describes a consistent feature of human moral judgment. There are, however, several rival theories of its psychological cause. I review these theories and consider their...

BACKGROUND Early-life chemical exposure may influence immune system development, subsequently affecting child health. We investigated immunomodulatory potentials of polychlorinated biphenyls (PCBs) and p,p'-DDE in infants. METHODS Prenatal exposure to PCBs and p,p'-DDE was estimated from maternal serum concentrations during pregnancy. Postnatal exposure was calculated from concentrations of t...

The northern aplomado falcon (Falco femoralis septentrionalis) disappeared from south Texas in the 1940s. Due to great success in the release of captive-reared aplomado falcons in south Texas, there are currently more than 40 established nesting pairs in the region. Addled eggs from aplomado falcons nesting in northern Chihuahua and south Texas were analyzed to determine organochlorine (OC) and...

Surface water and sediment samples collected from Jukskei River in South Africa, were subjected to different extraction techniques, liquid-liquid (LLE), solid-phase extraction (SPE), activated carbon extraction (ACE) and soxhlet extraction (SE) for sediment. The samples were extracted with dichloromethane, cleaned in a silica gel column and the extracts quantified using a Varian 3800 GC-ECD. Th...