Abstract The nature of the total water hardness distribution in river has been studied. It was found that during year, changes largely depend on seasonal factor, therefore, an analysis indicator separately for each month also made. Empirical functions were from built-in variational series. obtained laws differ normal and lognormal distributions, but are described quite accurately by gamma distr...

The purpose of present study was to evaluate fluoride, nitrate, iron, manganese and total hardness in drinking water of wells and reservoirs in Fereidonkenar, Mazandaran, Northern Iran and compare the results with national and international standards. This cross-sectional descriptive study was carried out on data during five years from the spring of 2008 until the autumn of 2013. Studies were p...

Recent evidence suggests that voluntary rhythmic movements such as chewing may increase blood serotonin and subsequently brain serotonin, which in turn acts to alleviate premenstrual symptoms. In this observational cross-sectional study, we tested the hypothesis that hardness (difficulty of chewing) of the habitual diet (i.e. dietary hardness) is associated with decreased premenstrual symptoms....

The effects of humic acid and water hardness on acute cadmium toxicity and accumulation were determined, using Puntius gonionotus Bleeker. The toxicities were expressed as the median lethal concentration (LC50) and the 96-h LC50 value of cadmium was 2.30 mg/L. Three different types of water hardness were used: soft, moderately-hard and hard, with total hardness concentrations of 55, 113, and 22...

Experiments were carried out on the survival and growth of Rasbora daniconius, Puntius ticto and Puntius conchonius. The motivation of the study was to obtain information for growing the fish on a commercial scale for their use as biological control agents against mosquito larvae. The effects of temperature, total hardness, DO, pH and feed on the growth of fish were also investigated. Excessive...

INTRODUCTION For the construction of any dental prosthesis, accurate impressions are necessary. Hence, we undertook the present study to evaluate and compare the surface hardness of gypsum casts poured from impressions made using conventional alginate and self-disinfecting alginate. MATERIALS AND METHODS A total of 30 impressions of stainless steel die were made, out of which 15 impressions w...

Formulas governing fixed orbital hardnesses and their relation to the hardness kernel are derived. It is shown how the orbital hardness matrix and its inverse matrix, the orbital softness matrix, may thus be directly calculated, and then the total chemical hardness, softness, and electronegativity of a molecular species. These quantities are calculated for the molecule HCN, using Dirac exchange...

In this paper we study the small Na+N (N 12) cationic clusters fragmentation channels, with all electronic calculations performed at the B3LYP/6–311G+(d,p) DFT level of theory. For these cluster sizes, we obtain for all neutral, cationic, bi-cationic and anionic species the optimized geometries, total energies and electronic properties such as the adiabatic ionization potentials, electron affin...

PURPOSE Light units used for polymerization of resin composites are subject to deterioration with age, and frequent maintenance is required to maintain optimal efficacy. This study examined the efficacy of quartz-tungsten-halogen light units in private dental offices in Toronto for polymerization of resin composites. MATERIALS AND METHODS One hundred dental offices met all selection criteria ...

AIM The aim of this in vitro study was to evaluate the surface roughness and hardness of both unbleached and bleached (opalescence; 10% carbamide peroxide) human enamel brushed with water (without dentifrice), fluoride abrasive dentifrice (Colgate Total) and whitening dentifrice (Natural White). MATERIALS AND METHODS Human enamel samples were obtained from third molars and randomly divided in...