Metal contamination in urban, suburban, and country park soils of Hong Kong : a study based on GIS and multivariate statistics

2005-2006 > Academic research: refereed > Publication in refereed journalAccepted ManuscriptPublishe

A collaborative change detection approach on multi-sensor spatial imagery for desertwetland monitoring after a flash flood in Southern Morocco

© 2019 by the authors. This study aims to present a technique that combines multi-sensor spatial data to monitor wetland areas after a flash-flood event in a Saharan arid region. To extract the most efficient information, seven satellite images (radar and optical) taken before and after the event were used. To achieve the objectives, this study used Sentinel-1 data to discriminate water body and soil roughness, and optical data to monitor the soil moisture after the event. The proposed method combines two approaches: one based on spectral processing, and the other based on categorical processing. The first step was to extract four spectral indices and utilize change vector analysis on multispectral diachronic images from three MSI Sentinel-2 images and two Landsat-8 OLI images acquired before and after the event. The second step was performed using pattern classification techniques, namely, linear classifiers based on support vector machines (SVM) with Gaussian kernels. The results of these two approaches were fused to generate a collaborative wetland change map. The application of co-registration and supervised classification based on textural and intensity information from Radar Sentinel-1 images taken before and after the event completes this work. The results obtained demonstrate the importance of the complementarity of multi-sensor images and a multi-approach methodology to better monitor changes to a wetland area after a flash-flood disaster

A nanoleakage perspective on bonding to oxidized dentin

The mechanism responsible for sodium-hypochlorite-induced reduction in dentin bond strength and its reversal with reducing agents is unknown. This study examined the relationship between nanoleakage and reversal of compromised bonding to oxidized dentin. Acid-etched dentin was completely depleted of demineralized collagen matrix when sodium hypochlorite was used. Specimens were bonded with two single-bottle dentin adhesives. They were immersed in ammoniacal silver nitrate for 24 hrs before being processed for transmission electron microscopy. For both adhesives, tensile bond strengths of acid-etched dentin were significantly reduced after sodium hypochlorite treatment, but were reversed when sodium ascorbate was used. After sodium hypochlorite application, reticular nanoleakge patterns in hybrid layers were replaced by vertical, shag-carpet-like patterns along the demineralization front. This type of nanoleakage was completely eliminated after sodium ascorbate treatment with the materials tested. Residual sodium hypochlorite within the porosities of mineralized dentin may result in incomplete resin polymerization, and hence compromised bond strength.published_or_final_versio

Aging affects two modes of nanoleakage expression in bonded dentin

Water sorption into resin-dentin interfaces precedes hydrolytic degradation. We hypothesized that these processes are morphologically manifested by the uptake of ammoniacal silver nitrate, which is thought to trace hydrophilic domains and water-filled channels within matrices. Water sorption is thought to be nonuniform and can be traced by the use of silver nitrate. Human teeth bonded with an experimental filled-adhesive were aged in artificial saliva (experimental) or non-aqueous mineral oil (control). Specimens retrieved for up to a 12-month period were immersed in 50 wt% ammoniacal silver nitrate and examined by transmission electron microscopy for identification of the changes in their silver uptake. Reticular silver deposits initially identified within the bulk of hybrid layers in the experimental group were gradually reduced over time, but were subsequently replaced by similar deposits that were located along the hybrid layer-adhesive interface. Silver uptake in water-binding domains of the adhesive layers increased with aging, resulting in water tree formation. These water-filled channels may act as potential sites for hydrolytic degradation of resin-dentin bonds.published_or_final_versio

Reversal of compromised bonding to oxidized etched dentin

The mechanism responsible for hydrogenperoxide- or sodium-hypochlorite-induced reductions in dentin bond strength is unknown. This in vitro study tested the hypothesis that these oxidizing agents were responsible by attempting to reverse the effect with sodium ascorbate, a reducing agent. Human dentin was treated with these oxidants before or after being acid-etched and with or without post-treatment with sodium ascorbate. They were bonded with either Single Bond or Excite. Hydrogen peroxide reduced the bond strengths of both adhesives, while sodium hypochlorite produced reduction in adhesion of only Single Bond (p < 0.05). Following treatment with sodium ascorbate, reductions in bond strength were reversed. Transmission and scanning electron microscopy showed partial removal of the demineralized collagen matrix only by sodium hypochlorite. The observed compromised bond strengths cannot be attributed to incomplete deproteinization and may be related to changes in the redox potential of the bonding substrates.published_or_final_versio

Reversal of compromised bonding in NaOCI or H2O2 treated etched dentin

published_or_final_versio

Reversal of compromised bonding in bleached enamel

Oxygen inhibits polymerization of resin-based materials. We hypothesized that compromised bonding to bleached enamel can be reversed with sodium ascorbate, an anti-oxidant. Sandblasted human enamel specimens were treated with distilled water (control) and 10% carbamide peroxide gel with or without further treatment with 10% sodium ascorbate. They were bonded with Single Bond (3M-ESPE) or Prime&Bond NT (Dentsply DeTrey) and restored with a composite. Specimens were prepared for microtensile bond testing and transmission electron microscopy after immersion in ammoniacal silver nitrate for nanoleakage evaluation. Bond strengths of both adhesives were reduced after bleaching but were reversed following sodium ascorbate treatment (P < 0.001). Resin-enamel interfaces in bleached enamel exhibited more extensive nanoleakage in the form of isolated silver grains and bubble-like silver deposits. Reduction of resin-enamel bond strength in bleached etched enamel is likely to be caused by a delayed release of oxygen that affects the polymerization of resin components.published_or_final_versio

Household dietary practices and family nutritional status in rural Ghana

A cross-sectional study involving 400 mothers was conducted in the Manya Krobo district of Ghana with the objective of studying household dietary practices, quality of diets and family nutritional status of rural Ghana. A combination of methods, including structured interviews using questionnaire, dietary assessments and anthropometry was used to collect data for the study. The data obtained was analyzed using Statistical Package for Social Sciences (SPSS) Version 10 in Windows. Means and standard deviations were generated for continuous variables and frequency distribution for categorical variables. Most women consumed meals three times a day but only a few (12.5%) cooked all three meals at home. Breakfast and lunch were the two main meals purchased from food vendors. The most frequently consumed food items on daily basis were the starchy staples, maize, fish, pepper, onion, tomato and palm fruits. The nutritional qualities of diets were poor in terms of calcium and the B-vitamins. A significant proportion of the women were nutritionally at risk of being either underweight (12%), overweight (17%) or obese (5%). For adequate nutrition in this population, nutrition education intervention programs aimed at improving nutrient intake through improved diet diversity and increased use of local foods rich in calcium and the B-vitamins needs to be undertaken. There is also the need to intensify education on excessive weight gain and its attendant health problems in the area

Assessing exclusive breastfeeding practices, dietary intakes and body mass index (BMI) of nursing mothers in Ekiti State of Nigeria

Breastfeeding is an unequalled way of providing ideal food for the infants. The benefits of breastfeeding practices to infants and mothers are well documented. However, information on breastfeeding practices and its effect on body mass index (BMI) of mothers are scarce, particularly in Ekiti State of Nigeria. Therefore, the present study is designed to assess breastfeeding practices and its association with BMI of mothers. A descriptive and cross-sectional study was conducted among breastfeeding mothers that attended postnatal clinic of the state specialist hospitals and maternity centers in the study location. The specialist hospital and two-third of the nine maternity centers were purposively selected because of their health facilities and personnel. The mother-child pairs (200 respondents) were randomly selected from the study locations. Information on demographic characteristic, socio-economic parameters, nutritional knowledge of breastfeeding and dietary intakes of mothers were collected using questionnaires. BMI of mothers was determined as described by World Health Organization. Age distribution of mothers was between 25-34 years; and almost half of respondents had good educational background and were engaged in different occupations. The respondent monthly income ranged between = N = 3500 - 26000 ($26.92 -$200); and their dietary intakes varied between starchy and protein-based food. The result also showed that the respondent consumed enough nutrients to meet up the recommended daily allowance for protein, carbohydrate, fat, zinc, magnesium, sodium and phosphorous requirements. The BMI classifications showed that over three-fifth of respondents were normal, while the remaining were underweight (6%) and overweight/obese (26.5%). Also, large proportion of respondents engaged in exclusive breastfeeding and with good knowledge of breastfeeding practices. Statistically, exclusive breastfeeding practices had no correlation between the BMI and frequency of breastfeeding. The study, therefore, concluded that mothers had good knowledge of breastfeeding practice; and that there was no association between breastfeeding practices and BMI

Increasing surface ozone concentrations in the background atmosphere of southern China, 1994-2007

Author name used in this publication: Wang, T.Author name used in this publication: Poon, C. N.Author name used in this publication: Lam, K. S.Author name used in this publication: Li. Y. S.2009-2010 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe